[AquaParade]

To me, the turtles can't really help but be killers. They were born into a loop of violence and revenge. It's part of their origin.

I think this tends to get ignored because it doesn't necessarily feel good to think about, and we want our turtle stories to be fun, alongside being dramatic, exciting, etc.

The fact is, the turtles being born into that never ending cycle of revenge doesn't make them "evil" or "bad". It's actually quite tragic..
They do their best to escape anarchy, or cut it off at it's root, but it mostly just perpetuates the violence.

By the time we roll around to "City at War", they want nothing more than to see a way out of it, even if it means aligning themselves with "The Foot".

The turtles/Splinter don't condone unnecissary violence, but they will do whatever it takes to protect themselves and their family. Like most everyone would.