Tom Sunic posts occasionally at the Occidental Observer. He correctly notes that speech in America is in no way free but is self-censored based on social and professional ostracism.
He attributes this to the usual subjects, and is right as far as that goes. But self-censorship seems to be deeply rooted in English-speaking societies. George Orwell mentions in his collected essays how it worked at the BBC in World War II. On a deeper level, he talks about how Jonathan Swift presented a consensus-oriented culture among elites in his portrayal of the Houyhnhnms, an elite class of horse people supported by primitive humans, in “Gulliver’s Travels”.
I don’t have the book handy and I haven’t been able to come up with a satisfactory way to express my thinking about it, but Orwell connects the emotionally constrained Houyhnhnms and their desire to maintain harmony among themselves over debate with the English elite, and I think this is correct. Elites can’t really afford much debate. Debate is for the relatively insecure. Different cultures and societies have different ways of maintaining control. English society has been very successful for centuries, and this must mean the English way of maintaining control is better. The SPLC is certainly good at letting people know what they can’t say, but their program only works because people have been conditioned for centuries to accept it.