Yes, I think us Brits defused many of our internal tensions as a mult-cultural AND classist society in the 70s and 80s with the transition from vaudeville racism to new-wave "alternative comedy". It didn't change the status-quo but it did move the dial toward more progressive ideas.
I do think HN is an odd place in it's intolerance of humour, and I don't see that "high bar" because TBH it's the lowborw geeky "knob-gags" that make the grade here in my observation. I think it's actually the old struggle of poets and philosophers (see Republic 2, 3, 5 [0]) is at play. HN adapts to filtering what it can't process. It's a bit like that AI brain in Blake's Seven that Villa causes to explode by feeding it riddles. I'm noticing even this "meta" talk about humour is being downvoted (and I hope those doing so are getting a good ironic laugh from that) :)
I've always seen this as a counterculture to Reddit, not as intolerance of humour.
I don't think HN actually hates humour, it just has a relatively high bar. Some of my most upvoted comments have been jokes. But I like to think they were reasonably good ones.
Regarding the Pythons and transgression, I think for me it's probably a case by case thing. There's obviously "good" transgression and "bad" transgression, but I suppose you have to have some support for the willingness to transgress, if you want positive social change to be a possibility.
Regarding specific things the Pythons said, the most actually transgressive-at-the-time thing I can think of is probably Graham Chapman's overt homosexuality and support for gay rights, which was no small thing in 1970s Britain.
Edit: Or you could make a case for it being the "blasphemous" Life of Brian, although I don't think the public outrage about that was really in step with mainstream opinion.
Edit2: I'm wondering whether Some Like it Hot, Milton Berle etc were considered transgressive in the US? Were these things not actually quite mainstream in the 20th century, even in the US?