Charley, what a great song! There are two examples of bad manners I just can't stand.

First, loud booing, hissing and attempting to hoot the musician off the stage is just poor. At least, people should let them finish the piece first, and express their displeasure afterward!!
Second, so far as I am concerned, spitting is very bad form. It's an abuse of hospitality to spit on the floor, I don't care what people say! But spitting on the musicians is INTOLERABLE. IMHO, people who spit the on musicians should be firmly told to leave!