The irony is that this person really has the "holier than thou" thing going on. What they're doing is just the worst excesses of religion by another name. Well you could say they're not actually genociding people, but that's because they're just a single person. Get enough like-minded radical communists together and it's going to turn out toxic like any other large gathering of people who think they're right and everyone else is wrong.
I have this hypothesis where people after a certain age are assholes because of who they are, not who they worship (even if it isn't strictly a god per se). You don't need a book (religious or otherwise) to tell you to be an asshole, it sorta just "justifies" the assholery. People like that are good evidence of such.
Assholery is an equal-opportunity condition. That's why you have the Westboro Baptist Church on one end, a seething, hateful group that sees only evil in others, and then you have good and "normal" Christians, who tolerate and respect others for who they are. Assholery is not something a large group has as a whole. As you said, it's the individuals that gang up and form cliques of assholes that cause problems for the rest of the group.
My hypothesis states "after a certain age", though. That's because children are malleable. You can teach whatever you want to them, and they'll believe it. This is why you have children who say shit like "black people should go to hell" or "LGBT people should all die" on certain platforms intended for kids. The parents of such children (and probably their friends and bullies) have these horrible values that they end up passing on to their children. And that's really bad, because most of those kids will end up being future racists and homophobes (in other words, assholes) because they lack the ability to question what they've been taught.
Why do you think I'm asking questions about sexuality and gender in the Random questions thread? I'm trying to push against my upbringing. I realized that my parents would probably disown me if they knew my true sexuality, so I'm educating myself now so that I don't end up repeating this cycle of homophobia that's been going on for generations. I don't care that I have to tear down years of assumptions. I'd rather do that now than end up being an asshole to others later on, even if it is by accident.
And that's the saddest part. Most assholes don't even know that they're being assholes. They think they're being "cool" or "upholding tradition" or some shit like that. They don't understand that their beliefs are hurting others. Hell, I'm not discounting myself here. I'm sure I've been an asshole before, either here or elsewhere, and I deeply apologize for that. All I can do now is make peace with what I've done before, and move on, hopefully as a better person.