Staying on the BNP issue for one more post, I really do question the argument that has it that the rise of the far Right is a reflection of the failure of mainstream parties to address legitimate concerns. If that were the case then presumably the problem in the 30s was that mainstream parties weren't addressing legitimate concerns about the Judeo-Bolshevik threat.
Personally I think that some of the concerns that lie behind the growth of the BNP are similarly bollox. Therefore the last thing that mainstream parties ought to be doing is legitiming concerns that may not have much basis in fact (ie the threat of Islamification, immigrants getting priority for council housing etc). The problem is, of course, that even when politicians do hold the line against misconceptions, these concerns persist, and there is always someone on hand to keep stoking the fire.
Flipping forward, the more people that start to accept the BNP view of immigration, the more likely they are to end up talking to others that share their view. And, if we accept Cass Sunstein's argument, this is likely to lead to reinforcement and a tendency to even more extreme positions.
To me it looks like the political equivalent of a speculative bubble. And unfortunately I suspect our ability to detect and try and deflate bubbles is likely to be as successful in politics as it is in economics. At some point the bubble will burst, and those caught up in the mania will look back on it with regret, but at the moment to many in the midst of it it must seem like it must be well-founded because look at all the others who agree.