I'm sure there are some HN users who just downvote everything they disagree with. However, I also think commenters with “minority opinions” need to realize that

I'm sure there are some HN users who just downvote everything they disagree with. However, I also think commenters with “minority opinions” need to realize that the onus is on them to justify what they say. A comment which says “the earth is round” does not and should not need to justify that position. Most of the community already thinks the earth is round, so commenters don't need to spend time explaining why. By contrast, a comment which claims “the earth is flat” had better damn well include why the earth is flat, and that argument had better be pretty convincing! Who knows, perhaps the flat-earthers were right all along and one of them will open my eyes some day—but the onus is on them. To take a more realistic example, I’ll sometimes see HN comments which are (in my estimation) based on the premise that government is inherently evil. Perhaps this is just an accepted truism in conservative circles, but it's not in mine, nor is it something I believe. So if I see a comment which assumes "all governments are bad" as a starting point, I will likely downvote it! (Please, let's not turn this thread into a discussion on the merits of government, I just needed a real-world example.) My goal is to downvote stupid arguments and upvote constructive ones, regardless of whether I agree—but due to the above, the two end up being correlated in practice.