this is picking up on a narrative that i've written a lot about on my blog going back quite a few years. and, while there's something to the idea of neo-liberalism co-opting the centre (i think that's the exact phraseology everybody here is aspiring to articulate and isn't succeeding in), the truth is this goes back quite a ways to a basic divide on the left between progressivism and socialism, which somehow got confused with each other when they built an alliance against neo-liberalism in the late 90s. if the democrats have been co-opted and taken over by neo-liberalism, socialism has likewise been co-opted and taken over by progressivism.
if you look into history, progressive politics was never this thing about labour rights, or sexual freedom or free speech or any of it. progressives have historically been culturally conservative religious types looking to bring back a golden era of puritanism. progressives have historically opposed capitalism not for the economic or social reasons that socialists do, but because commerce is a tool that satan uses to control the world. they've historically been horribly racist as well, pushing eugenics and other pseudo-nazi policies. the first sterilization laws weren't written by hitler, they were written by progressives from california. and, they've historically been absolutely vicious in their suppression of speech, mostly for religious reasons. taibi dropped tipper gore - but she was in the tradition of american progressivism!
when progressives got elected, they looked like woodrow wilson (who put the leader of the socialist party in jail) and theodore roosevelt (perhaps the most viciously openly colonialist president in american history). large amounts of what fdr had to do was undoing what these progressives did, especially with the good neighbour policy.
in canada, the progressive party actually merged with the conservative party, and people have long been confused by that, but it makes a lot of sense given that they were both rooted in christianity, against godless liberalism. they saw their shared religious values as the most important thing. a second progressive party - the ndp - still exists, and was built by one of the worst bigots that's ever held office in this country. he gets credit for building universal healthcare (which is false. tommy douglas' system looked more like obamacare. universal healthcare in canada was built by liberals copying the nhs, in britain.), but he was also thrown out of his own party for his bigotry against jews and gays.
the history of american socialism is a different thing. it doesn't involve middle class farmers banding together to fight against satan and reassert christian values, it's a struggle that existed in the workplace. and, if we're to get past this and make sense of it, we need to reassert this separation between socialism and progressivism, and reunderstand progressivism as a movement that has been socially conservative from the start.