I really like this policy.
I went to check out the chelsea forum the other day and it is so much the opposite of this classy website. Many of them are using the forum for random ranting and namecalling. There was a thread (on Lukaku or Courteois, I forget) and the last three pages were just two 'fans' calling each other all kinds of swear words, once or twice interrupted by other fans who actually wanted to state something regarding the thread.
I think that if you allow impolite language on this forum you eventually hinder the dialogue between the fans, because one fan will be offended by another and then the verbal feud will ensue and the many insulting messages will clog the thread.
Plus there's already so much foul language, hatred and bitterness on the internet fora ... and it is just a game after all. It is the most important non-important fact of life.