What idealists like Hange don't understand is that you don't do business with racist, especially if they are racist towards you. She obviously does not think about what happen after they actually kill Eren (they can't reason with him either, as that girl whose name I don't care about correctly said). And what would happen is that those subhumans like that scum Marleyan general would accuse her of something, rape and kill in prison, that's it. Not because it's dark and edgy but because they think that if you are born Eldian, you are not human and you can be treated as badly as anyone wants.
I just have realised, after I actually thought about it, that people from the island don't know what "nation" means, they think about all people as just "people", and they are reacting to Marley as just to temporary enemies because of misunderstanding. No, other countries on the planet have nationalistic mentality and are conditioned from birth that Eldians are less than humans, and they should be treated inequally just by the fact that Eldians are born Eldians. This is pure racism and this is incurable. People with this mentality should just cease to exist.
Eren stopped caring and decided to write off anybody outside the walls who is not actually racist as collateral damage, that's all. Morality of this action is questionable, but the goal is completely just. If you think that you can diminish the value of some person because of their birthplace or bloodline - drop dead, you have lost your right to live.
This is not a question of "some feud from 2000 years ago", it's totally in the question of "they are Eldians and we are Marley", that's it.