I think it's just sheltered people that didn't (/weren't forced to) discover all the possible evil in human behavior.

Lots of people grow up in a decent environment, without many major problems. If that is the case, it is very psychologically disadvantageous to become aware of all the evil possible by literally everybody, because this realization is extremely painful.

Ignorance is bliss and so on. Active, willful ignorance works just as well because our mind is so good at compartmentalizing. People like this can actually unconsciously be actively ignorant, because even the action of trying to be ignorant can be ignored successfully, that's how "good" at that the human mind is.

Because of that, in my opinion, your kind of comment is a little unhelpful. You're entirely right of course, but you phrased it relatively aggressive/as if it was completely obvious, as if you think people that don't believe that should feel bad. But I think the correct approach is to point your message out in a neutral/compassionate way, to make it easier for these ignorant people to read and feel less psychological pain, triggering less of the mental defenses. In any case though, I personally appreciate you :)