There seem to be two predominant types of Rush listeners:
1) Mainstream and often thoughtful conservatives who listen to Rush like a Hispanic listener might enjoy hearing "'Spic" humor from a fellow Latino comedian -- i.e., one of the fold, even when rude or abrasive.
2) The kind of "conservatives" who wouldn't spit on a cross or burn a flag, but will gladly slap a mouthy woman or put a {insert racial epithet here} in their place. This group seems to think listening to Rush is somewhere between listening to the news and listening to a prophet.
I couldn't guess what the actual demographics are, but I seem to meet about half and half. Plus a few liberal listeners who preplexingly seem to listen to Rush merely to work themselves up into a good angry fit. I can't stand to listen to the man myself; his voice makes the hair stand up on the back of my neck and I personally put his ranting into the potty humor/dumb blonde joke category, which I've never found the least bit amusing.
Rush at least seems to be winking at the audience from time to time, and his verbal abuse seems to be crafted for effect rather than 100% serious. There are far worse out there who seem to be under the delusion they are journalists.