What you said is sadly true for many subreddits. I can offer up /r/askhistorians as a counter-example though: a very well moderated subreddit with excellent historical discussions.
Just yesterday, /r/askhistorians had a question about Mother Theresa and it was one of the most level-headed discussions of her and her legacy I've ever seen. Especially since her death she's been almost the definition of a polarizing figure: people see her as either a saint or a sadist. They rarely acknowledge any middle ground.
Also, the hottest threads on those subreddits are almost always fresh things that you've never thought of before and it's very interesting to hear the answer from someone who studies the field in-depth (and provides sources!)