Because 1) conservatives rarely bother to speak up on HN; they know they are quite unwelcome here and 2) the illiberal left claims to be allied with liberals and that's clearly false.
That's actually the label the left has taken on themselves, blaming conservatives for it is really weird. Yes, the behavior of the modern left has little to do with the classical liberalism, but it's not the conservatives' fault that the left took on themselves this mantle and then failed to live up to it.