Car horns are a Pavlovian device that trigger jerks into action.
For some reason just the sound of a car horn turns some people from normal to angry jerk in a heartbeat. Maybe it is a defensive response to a perceived public accusation of doing something wrong or stupid.
The car horn is good for warning "Hey, you are about to hit another vehicle" but they sometimes produce a bad reaction when used afterwards as a rebuke for "Hey, you almost hit another vehicle".
That's right. Big difference between a short "wake up" beep and a long "eff you" beep.
I think one should think very hard about not using the horn at all if it would appear that you could be trapped in place by the offending driver. As stated above, you can't possibly know who you might be dealing with.