I don't have this experience on HN really. I suspect I'm closer to the average age here. There is the occasional poor opinion but it usually gets downvoted pretty hard. Even people that I disagree with I learn a lot from. Today in this thread I learned about how classic Christianity thought about doubt for example. Of course a lot of people are anonymous here (including me) so people are much more bold with their opinions than they would be in person.
Not discounting your experience, but to me I have a very different experience on HN than I do Reddit.