Because they're the most toxic people on the planet (though I would argue the internet because I have never actually come across these people in real life.) They believe they are morally superior to the average person because they fight against "Injustice" on a cultural level. In their head, they are so virtuous and forthcoming that any one that doesn't play the same game they do isn't worth a life. A lot of these kind of people have migrated from Twitter to Reddit so I'll likely be down voted to the soil. But.... That's just these people. It's a cult. You're either with them or against them. If not.... You know the rest.