It might sound silly that clothes can alter people's behaviour, but not only does it act as a uniform by which people recognise others like or unlike them, it can give people a pattern to model themselves on. I've just been reading a book by Joe Simpson (a mountaineer) in which he mentions someone in his local pub in Sheffield who went from business attire to shaven head, bomber jacket etc (this was the 1980s) and started picking fights. Then later, after one too many fights, reverted to his previous mode of dress and meek and mild behaviour.
Of course those dedicated to violence will simply change their uniform, within certain broad limits.
