Of course I agree United was wrong in that they should not have bumped passengers, particularly after they had already boarded, to accommodate employees. That was the fundamental error.

But the customers' reaction was also not right. The other three passengers deplaned peacefully even though they did not want to, which was what a mature adult would do.  Refusing to deplane so that police have to carry you off  is NOT something to be applauded, no matter how wrong United's policy was. "Air rage" is not a proper response, two wrongs do not make a right.