Believing that there are some rude and disrespectful BYU fans is easy to believe.  However, it's really hard to believe that "most" BYU fans act this way unless the BYU fans around you are not representative of the general population of BYU fans.  Either your claim is an exaggeration, or you attract rude BYU fans, or you have an abnormal sense of what consistutes rudeness, or it is in fact true that most BYU fans are rude.  I suspect it's not the latter, since when I look at cougarboard, which has an elevated level of rudeness compared to most BYU fans I know, I still wouldn't characterize most cougarboarders as rude.