Why do some posters believe they have to educate you against your will?

A lot of people derive their sense of self-esteem from feeling smarter than or superior to other people. It's unfortunate that they can't see past whatever personal issues they have to see others as just people.

The fact that they spend as much time as they do online probably means they're socially isolated, so they may need to derive their sense of value from doing things like that. They get lost in these culture war issues because being on the "good" side is likely one of the few things that makes them feel good.

Just my two cents as someone that used to struggle with loneliness and insecurity

I resent religious fanatics going into forums that aren’t about religion to proselytize. It makes it harder to avoid them.

Over time, I tend to ignore and mute those people if what they post is repetitive and unhelpful.

Indeed. They think they are smarter than they actually are and have the insecure need to prove it.