He thought he was clever because he thought (wrongly) that he was sounding reasonable. That he was making valid or scientific or factual 'points'. His friends knew better. And I got the impression they'd heard this or similar idiocy from him plenty before. There was a weariness in their entreaties that he shut up, that he was being rude and offensive that suggested they'd seen him making a prick of himself all too often.
Personally if I'd been them I'd have cut his ass loose a long time ago. I shut down and shut out scumbags before for being sexist or racism or ableist.
He was simply proof that no section of society, no demographic, no community is without its dickheads.