As someone with an outside perspective, I can honestly say that there's a major difference between "Killing out of absolute necessity" and "Killing for SCIENCE". So you can stuff your moral myopia down your throat as you die hood man.
Generic strong mc with weak mindset then takes some chapters of flashback about the new friends that tells him he's kind or something then he bounces back to the battle with "resolve"
It's the hentai AND the twisted mind of these readers. I didn't connect that to those thoughts at all.
I was actually thinking about the gruesome death those classmates he saved faced. He probably killed them off to not share his secret identity of superman.