I totally agree with all the others here that have been saying, BOFH to those that are being inconsiderate. Bottom line, don't take the crap. I work for a small Medical Clinic and had a doctor yell at me and tell me, "You need to fix this now and I don't have time to tell you whats wrong with it" which to my reply was something along the lines of, "Well how do you expect me to diagnose the problem then?"
You'd really think that of all people, Doctors would have half a clue. This is just not the case, and I don't think most will.
What works for me and my co-worker is having a real strict web usage policy. We already block most of the fun stuff by default, so whatever's left is for them to play with. The first time they wind up on the virus alert, they are warned with a CC to their manager. The next time, the entire internet is taken away from them. Since I've started holding to this more strictly, in some cases the virus may have been a false positive, I haven't had people be as rude to me as they were before.
I think we get this kind of bad rap because you will usually walk into an IT room and see what appears to a user as us not working. Half our job in a day can consist of waiting though. Waiting for this to complete, or waiting for an issue you've been watching to replicate. Lots of waiting though. On top of that, none of them understand the maintenance behind the scene. I think that because a lot of what we do cannot easily be understood by most, when you so happen to come and ask for help and you just see us staring at a screen reading something it's assumed that you weren't working.
So all in all, if they are asking for your help because they actually broke something and are uncivil about it, take away whatever caused the problem. Elevated rights, surfing abilities, lock them down so tight that they wont need to come ask you for help because you've tightened the leash so tight that the only problem they'll have is with whatever 3rd party business software you use and nothing you can really control besides doing updates or calling vendors.