I mean, it's pretty safe to assume that the overwhelming majority of people are against racism, whether it be the theory or the practical application.
It seems about as sensible as declaring yourself an 'anti-rapist'. Yes, that's great, but we all think it's wrong too, it's just a little bloody obvious, so why make a point of it.
I guess the reports of the LM,HR event in London brought this to mind. That said, I love the thought of a bunch of white people who would never dream of voting BNP chanting 'Fuck the BNP' in response to some other white people urging them not to vote for...errr...the BNP.