Perhaps if you are disgusted that they got in because of the population's apathy, you should focus your energies on challenging that apathy?
Don't get me wrong, there was a 30% decline in turnout for my area compared with 2005. That is shocking.
But get rid of the BNP, and there will be another party by another name with the same politics to take its place.
As long as they don't break any laws, they are entitled to stand for election. They did, and they were.