I've been lurking the various Poligaf threads for many years now. I don't think I've ever seen a mod silence anyone for their political views. What I have seen are several situations in which a single conservative posts, then is flooded with responses- about their opinion, why they think that way, and with counter-arguments.
And a lot of the time, it seems that those conservative posters have a tendency to crack under the pressure, eventually saying or doing something worthy of a ban.
Overall, I think Poligaf is actually pretty welcoming to people of many views, so long as that person is able to back up their beliefs with something more than "it was how I was raised" or "because the holy book of my choice says so" or "talking point #587".
And I'm saying this as someone who originally found GAF when he was a stringent member of the religious right.