Actually, I think they all know how horrid the Yoko thing was but were just making fun of Katy Perry. But you're right, it's a slightly older crowd (for the most part) at the SH Forums and a lot of them are died hard Beatles types. Plus, they hate pretty much anything that has happened in the music world from Madonna forward and certainly would not think it's "cool" to like Katy Perry because it would go against their code as much as would drinking a Bud if you're a beer douche.
I'm personally indifferent to Katy Perry. She does seem at least marginally talented as a vocalist in a plain vanilla kind of way, and has put out some well produced music, plus she comes across with a great desire to be wholesome (she referred to herself as an All-American Girl twice in the interview segment they aired during the game) and I'm not at all opposed to that as a change to pace these days.
Felt bad for the people in the audience at the Yoko thing who all (I'd hope reluctantly) applauded at the end of it. Yes, I forced myself to watch the whole thing.