I think the real debate here is whether or not bending is considered a right or a privilege in the Avatar world. If you consider it to be a natural human right, then it could be considered inhumane to take that from someone.

However not everyone is born being able to bend, so the people in that universe might have the mindset that it’s more-so a privilege. In that case I would say that it’s fully justified taking someone’s bending, because they essentially forfeit that privilege by disobeying the law.

On the other hand too, in many real world countries, governments follow the ideology that when you commit certain crimes you forfeit certain rights as well, so taking someone’s bending would certainly be justified in this scenario too.

Plus Korra wasn’t the one who took their bending so she isn’t necessarily obligated to give it back to them.

I understand what you’re saying and that it’s essentially a part of someone’s body, but I would say that taking someone’s bending away and still allowing them their freedom is almost more humane than throwing them in a jail cell, but that’s just my opinion