I just don’t think that’s the case here. I see comments get hidden because they violate the site rules on stereotyping or victim-blaming or name-calling, not because they’re (usually also) expressing a politically conservative point of view but because right-wingers tend to do those things more often than left-wingers do. As often as they’re flagged here, they’re pushed back at and refuted in replies – either way, neither is suppression of conservative political viewpoints in general.
That said, there’s no doubt that the commentariat here tends to lean more to the left socially and economically. Not surprising, given that BB’s publisher and Authors lean in the same direction. And while liberals and progressives are certainly capable of violating the site rules as defined by the site owners and enforced/interpreted by the mods with the help of the Discourse system, they just don’t end up doing that as often as modern conservatives and capital-L Libertarians do.
What really frustrates certain people with “unpopular” or “contrarian” views that violate the rules is that this BBS platform, in contrast to most others, has both highly professional and highly involved moderators and a system designed specifically for and based on feedback from said moderators. Furthermore, the regulars here, who seem to have decades of experience on various forums, are well-versed at spotting all the shoddy tricks they pull and aren’t afraid to call them on it or flag them. Between all that they can’t get away with the behaviour they’ve been able to on other forums.