I can't help but notice that those expressing right-wing and/or reactionary viewpoints, even when they weren't even trying to rationalize them, but presented them as fact, have been treated in a much more forgiving way, and I'm having trouble understanding why.

I've been explaining some radical right-wing views here, true, but I've also more or less expounded my own leftist views (in an ideological way, not a political one - there's a difference) and have been upvoted for it :) Don't worry, there's no dark conspiracy on LW, the right-wing/libertarian/generally contrarian people you see around these parts are just the cream of the crop for several reasons of selection. If you try and achieve their level of eloquence and writing quality, even for the duration of one post, you'll get plenty of karma and attention.