swim through the fires to stay in this world

Yeah, and given the constraints of a Nick show marketed to such a young audience, I am constantly astounded at how much they DO get away with. There's genocide, and brain-washing, and a creepy secret police, and plenty of character deaths and injuries (just discreetly bandaged, off-screen, or otherwise non-bloody), and hints of racial/cultural prejudice, and refugees...really, for all that they have to play some of the darkest stuff with a very light, subtle hand, they're still managing to give a surprisingly good portrait of life under siege/occupation. Even with all the magical elements, this is still very clearly a world where violence has lasting consequences, and people aren't just going to shrug off their injuries like action-movie heroes. And that even extends towards showing the mental/emotional toll -- Aang's anxiety before the invasion, Jet's and Hama's unreasoning hate towards even FN civilians... There are still a few things that you would expect to be coming up in this sort of wartime setting, like rape or more direct forms of torture, that I'm sure will never ever be dealt with directly since it's a kiddie show, but the world's been portrayed with such realism that an adult viewer can imaginatively fill in all the little dark corners for themselves.