AWKWARD ZOMBIE

yes, sped up, and dubbed over

if you note the original, you can hear their bones straining from the stress of being forcibly knocked unconscious.

In the books released to be between the two series (the promise trilogy, mostly), Aang is pressured by the Earth King and the past avatars to "restore the balance" of the nations by forcibly separating them out, like all of the previous Avatars did to restore balance. Aang is one of the first avatars to question whether the antiquated notion of the 4 nations being separate really helps, since everything is stagnant and exchange of culture is stifled and suppressed.

Aang did a lot of things avatars weren't supposed to. He didn't kill Ozai, he chose love over his duty, and he let the nations mingle rather than keeping them distinct. It goes with the Avatar learning from people and growing closer to being a more perfect guardian of them rather than a soulless automaton dishing out the laws of the world.

The world did advance with Aang gone for 100 years, but it was all one-sided by the fire nation, and easily could have been completely undone by Aang if he wanted to. We have no idea how much technology may have fluctuated over time. However, we can see how much its flourished with the current mixing of the nations.

And about bloodbending, every type of bending can be used violently or non-violently. Airbenders could pretty much kill anyone by suffocation or even shredding them with air if they wanted to. Bloodbending seems difficult and mostly painful because waterbending usually is about restricting and controlling the fluidity of water. If your blood suddenly stops in your body, it doesn't know how to react. There's presumably a way to bloodbend without causing harm to the person you're bending, but that's a high level ability, and the most notable bloodbenders we've seen have been consumed by their ability to control their opponents while being unstoppable.

About the best way bloodbending could probably be used is either on oneself (taking blood out to fight like how Katara bended out her sweat in Season 3, or to force your body to move even when you're incapacitated), or to cessate the blood for an instant, just enough to knock someone off balance and capture them. Anything more, without the skill behind it, is dangerous, like playing with fire all willy-nilly.

Just because people use bloodbending for bad things doesn't mean that bloodbending is without good uses. And just because Airbenders have a moral code of self-defense, doesn't mean that the bending itself can't be violent and deadly.

You have to look at bloodbending and how it's used now. Because it's not always used to hurt for the sake of hurting, like how Yakone forced his courtroom to sit there in pain for quite some time, and it has been used to simply take someone out quickly and easily.
The problem is that doing so seems to involve several seconds of agonizing pain nonetheless.

It may have completely non-violent uses, and it could have potential, but so far every bloodbender hasn't used it like that.

It's also a direct opposite to another waterbending art, healing, so it's potential as a more helpful thing becomes even more limited.

Any person who could be incapacitated with bloodbending could also be incapacitated with waterbending. There's no reason why they couldn't be. So then bloodbending is almost always going over the top for the sake of power. That makes it a difficult thing to use nicely, as in general it would be used in situations where it's unneeded anyways.

Bloodbending seems really to be an inherently twisted act. It could have good uses, but so much less so than any other form of bending, because other forms of waterbending itself will always be more effective at peaceful things.

Waterbending also requires water to be present to be effective. Remember how useless Earthbenders were at the all-metal fire prison in season 1? Water benders are in the same position if they can't get creative. Not to mention, water is one of the easiest resources to try to restrict (can't get rid of air or earth as easily). Dealing with a waterbender? Lead them to fight you in a place where there isn't any water. They have the moisture in the air and maybe the water in the ground to work with.

Again, I think the main way bloodbending can be positive is if it's self-inflicted. Got no water? Rip out a pint of blood and go to town to stop the opponent (though at that point you probably should just try to carry water like Katara does or use urine or something, IDFK).

Still, I object mainly to the idea that it's wholly impossible for bloodbending to be used positively, and that airbending is something incapable of horrific actions. Hell, even energybending could be abused the fuck out of, which we kinda saw when Amon emulated Aang's technique to use it for personal purposes, and that was used to end a war and keep a dangerous criminal from causing more harm.

I definitely think bloodbending is too tempting for the majority of people to use well. It becomes a shortcut technique for them in lieu of other just as effective (if a bit slower and more variable) options. But, I think the emphasis of bloodbending establishes the users as a bit more... tragic, so far. Hama had to use it to get free from the Fire Nation, and had that been the last of it, maybe we would have seen her as a more positive character, though willing to do something grotesque to achieve her goal. However, the revenge she took against the people, and the kidnapping she committed showed that while she used to be a promising young creative bender (like Katara), she had become exactly what she was fighting against.

Then you have Tarrlok and Amon, who were forced to bloodbend by their father for the glory of their family line. Tarrlok felt a lot of guilt and anguish not only over having to do it, but also because of his weakness in not being commited to doing it. He had to build everything for the name of his father and himself, and ended up resorting to bloodbending when he was threatened by the very thing that stopped his father, the Avatar. Ultimately, he decided to (at least try) taking himself and Amon out to prevent their dangerous bloodbending from staying in the world.

There is no doubt that bloodbending has prehaps the greatest potential for abuse, but we could also see the theoretical vacuumbending, bonebending, or nervebending (bending the electricity in someone) could also be the bloodbending for the other styles. And we could also see how bloodbending could be useful or necessary. Katara was forced to use it to stop Hama or else her friends would have died. Maybe it hurt Hama, but no one died in the process. And Katara resolved to never use it again.

Bending is a dangerous weapon and an essential tool. As you said, waterbending is capable of healing just as it is capable of bloodbending. Bloodbending is just one aspect of the spectrum.

All this talk of bloodbending makes me wonder about the physical effects of it.

Say you stopped a person's blood from moving entirely, which seems like the plausible first step to bloodbending a person and seems to be the first thing bloodbenders do (or at least stop the person from moving entirely).

Meanwhile, your heart is still beating, and the rest of your body isn't getting oxygen. The body's first response to not getting that oxygen would be to increase your breathing and heart rate. Now your heart is working harder, but you're not getting any oxygen. Keep in mind the heart itself isn't getting any either. This is essentially a forced cardiac arrest.

If the bender were to hold that person there for a few minutes, they would lose consciousness. According to wikipedia, brain damage would start occuring after five minutes.

Now, perhaps once the bender starts moving the victim around, blood might start flowing again, but it seems like it would be difficult to bend water/blood that's flowing in all directions /and/ move that water around at the same time. It would take a lot of finesse, and since bloodbending is pretty high-skill already, it would surprise me if an extended amount of bloodbending could be done on a person in a non-harmful way.

Maybe if someone perfected the art and used it for medical purposes, but waterbenders already have healing abilities.

See, I can agree that bloodbending has potential purposes outside of physical harm, but the problem is that healing or basic waterbending already does most of it. There's so many ways that it could become necessary, but they're horribly specific and they rely on the idea that a waterbender isn't going to be carrying water around with them everywhere. That's the problem. It's so primarily focused on pain that it's beneficial uses are hidden really deep and are easily outclassed by the other forms of waterbending.

Also, I don't recall saying Airbending had no passive uses, but it's far more difficult to make someone immobile with air. It is probably the best for complete pacifism, being capable of redirecting attacks. Just not for a quick and painless takedown. I guess in theory you could suspend them in the air by manipulating the air around them, but that'd be very high level bending and would mean manipulating currents to keep someone locked in place and not just flying away.

I think one of the evils of Bloodbending is that it overrides and infects the spirit of the victim. Blood outside the body is easily bent, but inside it's still part of the victim. It's why it's so difficult to pull off. Most Waterbenders aren't strong enough to override their opponent's control. Amon uses Bloodbending to sever a spiritual connection. It's an attack on the soul. Healing is the opposite. It uses the target's spirit to help it do what it wants to do, recover.

One of the pros of Bloodbending is that you can subdue your opponent without externally harming him in anyway, rather than shooting a fireball at him, throwing icicles at him, throwing him into the wall with a gust of air, or sending him twenty feet up into the air with a rock shelf, or by accidentally giving him frostbite by freezing him in a block of ice.

It isn't hard to stop someone with earthbuilding, just encase their arms in rock, the frostbit bit is a good point but at least getting cold around your wrists isn't pain all over your body because your blood is being bent around inside of you you

Blood clots are immensely painful. I doubt Bloodbending less so. Perhaps it has non-lethal applications, but non-lethal means of torture are still prosecuted by the Hague.

I cant imagine anyone having the finesse necesary to not wreck the shit out of your body while using blood bending. Even if you survive, the shock to your system must be catastrophic

But can he make them do the Cancan?

All of those wolves may have bled out internally minutes later. Bloodbending was made illegal by Katara's decree, she may have made an informed decision.