Hehe i had a similar experience with colleagues when i was working. Was chatting to a friend who worked with me about a film i had seen the previous night on the Sci-Fi channel and another colleague was all 'wtf, you STILL watch cartoons etc' He was the typical lad who HAD to go out EVERY Friday and Saturday night to get completely rat arsed in clubs and made fun of those that dared to do anything different.
So i said that i would bring in a video the next day to show him that it was no mere cartoon. I took in Ninja Scroll, Fist of the North Star and a vhs of The Guyver
I put on The Guyver first and sat down with my mate and the other guy to have lunch and i had picked the episode where Sho gets his head ripped open by Enzyme and goes on a rampage, needless to say they were both shocked into speechlessness and just watched in wonder as i gave pointers.
My mate wanted to borrow Ninja Scroll and the other guy was interested in FotNS so i lent him that. Next day i couldn't get them to shut up about the films. They fucking loved them and wanted more ^^
In the following years i have tried to watch more diverse anime but my HATE of subtitles and general lack of knowledge in what are 'good' ones to watch, i fear i have barely even begun.
All in all it just boils down to their perception of what is the 'norm' and the reluctance to believe something else is just as good as what they like.