The worse thing you could do with the BNP and other extremist bigoted groups is to ban them make them seem daring to be part off to some.
Like the police do let them say in the public eye where they can keep an eye on them, they dont seem exciting to those who want to rebel.
Look at clockwork orange i remeber it being exciting to watch a video of when tyounger now since its shown on TV now and then its lost all the appeal.
Banning or stopping people do something often has the wrong affect it seems.
Im pretty Sure many young Muslim and White extremists just doing it to rebel. Many of their parents I bet were not sharing the same extreme views in fact more likely the opposite.
Make the groups mundane and out argue them whoever the bigots are.
