I don't see that at all. I am engaging with many voices on the other side [1] [2]. Those comments are voted down, yes, but not because "HN hates freedom" or some such, but rather because (a) those opinions are not well informed and (b) HN is broadly upper-class and educated, and therefore not tolerant of uninformed opinions. The only widespread bias I see here is towards constructive and intelligent commenting; and in the current political atmosphere, it's simply not possible to be both intelligent and Republican.
> I suppose that in their mind it's some sort of attempt at manufacturing consent.
What I see in your comment is you are upset that you are on the losing side of an argument and so you're accusing the other side of cheating. Hey, that sounds familiar!
> In the grand scheme of things we're likely at the tail end of the era where having genuine political discussion online was possible, if not already slightly beyond it.
You are probably right, but for reasons entirely unrelated to dumb comments getting downvoted on HN.