It wasn’t so much that there was a stigma against watching Monty Python per se. It’s that it became sort of inextricably linked with a certain type of kid who became obsessed with it, could (and frequently would) recite all the lines of the movies from memory, and would tend to be a little obnoxious about their fandom. They were usually nerdy kids who already weren’t well liked by the more popular cliques, and aggressively shouting lines from Holy Grail at people wasn’t helping matters. Like, my friends and I loved those movies, but I guess not as much as the theater kids who were galloping around the school on imaginary horses shouting, “Ni!” at people and demanding a shrubbery.