As said in the story; "Everyone is a devil in their own way" (or something like that, I don't clearly remember but you get what I mean. I think). The world of AoT is unfair and unjust, with people justifying their ideology to label it as "facts" like how the rest of the world called Eldians demons and such, even though they did nothing wrong. I agree when you say that it's understandable but in no way do I agree that it's justified (because that would mean that it's right). I mean c'mon, they fear huge penisless madlads (which is indeed very terrifying) but Marleyans don't vommit towards the act of feeding an innocent girl to dogs when in fact she just got dragged by his fcking brother to go see a fcking airship, then there's Hizuru, which you say is innocent and should not be included in Eren's plan of genocide, but think for a sec, do you honestly think that they built a good relationship with Paradis mainly to help them get acknowledged by the world?? A big NO because their main purpose was to get ahold of Paradis' resources and to get their kin back (which is Mikasa). Finally, there's Zemo (this point is discussed in another comment but I'll include it here) which was introduced to get the readers to sympathize the people who will die because of Eren, but then we find out that he pickpockets and even though it's to help his family, it's wrong. Zemo's circumstances is another example of something that is understandable but is also something that can't be justified. Again, everyone is a demon in their own way and the world fearing titans is understandable because humans fear death specially a painful one. That's the real reason why they loathe titans, not because they are the creation of demons or whatnot, they just say that descendants of Ymir are demons to "justify" their decision to annihilate them but in no way is it "justified" or "right" because they are also demons themselves. It's like a robber who got robbed wanted the robber to be put in jail.