The dude was an idiot. If they ask you to get off the plane, then get off and let everyone else go about their business without interruption. If you have some recourse, then pursue it peacefully later.

United Airlines probably acted stupidly as well. If you have an idiot who will not cooperate, then start offering money to others who are willing to do so. Didn't breaking that guitar teach how guys anything?

Problem solved.

But I also can't believe how interested people are in a story about a bunch of idiots hauling another idiot off a plane. I don't care that much.