The NF are now complaining the newspaper won’t accept any more advertisements.
I believe a newspaper owner has the right to accept or reject any advertising at their discretion. It is their newspaper.
Having said that, personally I don’t think banning their ads is an effective strategy. What I would do is make sure I place a big article on recent arrests of National Front members next to their advert. That way you take their money, and diminish the effectiveness of their ad.