in this case its less about them being an evil race and more that they're a group they are currently at war with, if they were humans they'd feel more guilt but it'd be the same shit
its not like they're just randomly killing demons, they killed 1 spy hiding in a school, 2 who came to attack them, 3 who were spying and planning on a mass attack against their capital, 2 who were being teleported outside the capital to attack them, and now 1 teleporting to the capital for a mass attack. i dont get whats even the point of talking about whether they're evil or whatever when they've already shown themselves to be enemies. save the debating for people who aren't currently attacking you or planning new ways to attack you.