Isn't this about prejudice?
Anyway, I'm an old fogie, I'm given time to most things and don't think I'm prejudiced about much. The one thing I won't give any time to is gambling. I haven't tried it myself, but too many of my friends blow their paycheck on it, and I just see it as a very negative thing, not something that you get your money's worth of enjoyment out of.
As for other things... well, I don't actually get excited about sport, but I like the fact it exists. It's very healthy and a great use of live TV. High culture... again, it's good that it exists. At the other end of the scale, I find people are very snobby about Simon Cowell's talent shows, but they can be great fun. Basically, I dislike snobbery, both conventional and inverse.
I quite dislike films, and won't give them a chance any more, but I've seen enough. I've come to the conclusion that Hollywood is about stuffing violence and gore down our throats, and I won't give it any more time. It's not an industry I support.
Oh, I do know one thing I'm prejudiced about: mainstream gaming. Not that I haven't tried it, exactly, but maybe I could get some enjoyment out of FPSes and such if they gave them a chance.
This is happening to me at the moment. I'm guessing your friend was not the brightest person? The people who do this seem to be the ones with not much going on in their head.