Clearly, anybody can sign up.
Equally clear is that certain people can pretty much expect to be at best condescended to, and at worst subjected to insult.
Those who may be at high risk for being treated like party crashers seem to include Christians, Republicans, Libertarians, laissez faire free marketeers, the Rich, Obama critics, global warming skeptics, 10nth Amendment believers, careless spellers and sloppy punctuators, anyone who tunes into Fox, moral objectivists, and others, too numerous to mention, but easy to identify.
I realize that nobody has to join, or stay for that matter. But is this a “Group-Think” site by design, or did it get that way by a sort of natural selection?