Repercussions for deeds not allegiances
It seems to me that it would be a grave injustice to dismiss anyone for their political allegiance. In effect this says that a member of a political party will be not be sacked for anything he or she has actually done wrong but what they might possibly do by virtue of their party membership.
Members of the BNP have rights just like the rest of us. It will not do to say that everybody has rights except ..... (insert unpopular political movement or religious sect of your choice) members. Their possession of these rights does not rest on their willingness to extend the same rights to us. You either have them or you don't. There's no middle way.
This is where the mainstream trade union movement goes wrong as they refuse to stand up for the rights of some workers and line up with the bosses to get them sacked. Thank God for the free Solidarity trade union.