Personal experience ofc, but a lot of people argue in bad faith. Knowingly (or unknowingly) invoke logical fallacies, whataboutisms and straw man arguments. With how ideologically volatile the internet has turned in recent years, you can't really have a reasonable argument any more without it becoming just a name calling session.

Yesterday I noticed just how much reddit had jaded me. Had a bbq with some friends and a guy I knew was very much in the right, q anon stuff and all, asked me about my position on polarizing topics. I'm anarcho syndicalist. Expected it to get heated. Dude just genuinely asked questions and that was it. No trying to prod holes into the ideology or show the superiority of his ideology. It was kinda eye opening and showed me I just spent too much time in toxic areas of the internet. Though he seemed to have a bone to pick with the stereotypical city dweller lib. Had I had those positions he probably would've unloaded with quotes from the usual suspect talking heads.

It helps prevent hivemind mentality and keeps us growing. Unpopular opinions often have ideas worth examining or could be outright correct despite common wisdom saying otherwise, and forums like these are one of the best places for us to engage with those facts. There's also times when an opinion we like dislike is misinformed, and rather than send it to the bottom, it's good to explain how it's wrong for both our own sake (refining our arguments) and bystanders that haven't given the topic much thought.

But if someone left a turd, send that stank to the bottom!