I just went to see the holocaust museum in D.C this week. They had a section on propaganda that was very interesting... I had always wondered how it was possible for a nation to suddenly become racist to such a degree... it struck me as scary that actually they were a minority party and that they carefully targeted each separate group of the population, telling them what the wanted to hear, in order to gain a foothold.
This is how the BNP works. I am horrified that my Nana and Granddad wanted to vote BNP in the local elections. Their decision was based on what they had read in those bastions of objective reporting, the News of The World and The Sun, and also on the policies that were shouted from loud speakers outside their home; more money for OAPs, more fuel allowance, better care and respect for the elderly. My grandparents barely even knew of the other policies, except a vague idea that Britain would take back jobs from the foreigners...
So, I think not all supporters are actually actively racist, but are guilty of ignorance and that it would only take a small jump to go from allowing BNP to have a few seats, to finding ourselves in the midst of another holocaust.