I do not think these people have any cause other that creating havoc and beating people up. They are the purest example of what I called gangster gratification in my earlier posting - rather popular in segments of the US society nowadays. The only difference between this element and the rest of the thrill and adrenaline rush seeking crowd is that most people are satisfied with virtual stimuli (movies, video games, music) whereas this element goes for the real thing.
Again, we live in times when anything loud, obnoxious and outrageous goes - there is no ideology or any meaning behind it - just the shock effect. The skinheads are the counterculture in its purest form.
Wojtek