The comment was uncivil because it was unduly personal. Also it was harsh and unsubstantive, and guilty of its own charge (making assumptions) to boot. All that makes for a bad combo. I realize you don't see it that way, but that's because we all misjudge how our comments land with others online.

Moderating this sort of thing is routine to the point of tedium on Hacker News and doesn't have to do with your specific views, let alone 'silencing dissent' (a rather bombastic phrase which I hear a lot, from every ideological quarter). It just has to do with people's tendency to attack each other on the internet, which the spirit of HN is to try to work around, in the hope of good and interesting conversation. That's all.

Actually these attacks mirror each other across all ideological divides. We moderate them routinely as best we can, and then people routinely accuse us of siding with their enemies [1], but (a) these claims are contradictory and so cancel each other out, and (b) I'm pretty sure the majority of readers trust that we're not biased that way—or at least not ridiculously so, because our job would be impossible if we were.

1. An example from a few minutes ago: https://news.ycombinator.com/item?id=15310419.