And pulls a trick I've never been fond of:
I found my way to his Twitter thread, and then went to the comments section of the article in question. Unless there is some other forum he's referencing, I saw nobody suggesting Karl Marx was alive in the 20th Century. Catholic or otherwise. Nor have I ever heard anyone say such a thing. I did find some commenters supporting Sam who posted goofy things. But I found nobody suggesting Marx was alive in the 20th Century. If you say 'these people seem to think', then show some quotes and let us make the call.
In any event, all of this might suggest that Sam, like more and more on the Left, is prepping to come clean about his views on Marxism, if not full blown Communism. He would hardly be alone. The last decade or so has seen a growing number of pundits, journalists, news outlets, activists and others extoling the virtues of Marx, Marxism, Communism and Communist states.
At least they're letting us know what we're up against. If it ever becomes the default ruling ideology of America, the results won't be any different than they have been anywhere else. Only this time there won't be an America to oppose it.
I found that assessment of people who disagree with Sam rather telling. IMO, it says more about Sam and how he views religion, than these people he references.