I agree. What jerks. Some riders have to get a clue if we want the driving public to treat us all with respect.For me personally, skip the friendly toot of the horn. If you must, don't do it until you have already passed me.
Now I must admit I really want to lay it on the horn at times when I get behind a pack of racers heading down a major two lane road 3-4 abreast and will not pull single file and traffic is backed up 4+ cars deep. To me, that is unsafe, rude, and perpetuates motorists bad attitudes toward all cyclists.