Other users have already made some good replies, but I want to add that this is an example of what I wrote about in https://news.ycombinator.com/item?id=23308098 and https://news.ycombinator.com/item?id=35932851 (one's feeling of good faith decreases as the distance between someone else's opinion and one's own increases). The community is much bigger than people assume it is, and therefore contains a much wider range of backgrounds and views than people assume it ought to.

I believe this is the main factor that tricks readers into assuming that (legit) comments and votes on a story must be manipulated. It's hard to fathom how anyone could in good faith hold views so different from one's own, views that seem not just obviously wrong but monstrous.