People can figure out from context what four letter words are being used and they think, to paraphrase Louis CK, "Oh, they're saying %%%%%%" That's how language works! Also, this language is not obscene. There is no obscenity other than that which we create. If this is about expression and emotion is being expressed, why censor the words? The words are only vehicles for emotion. Seems like a very dishonest move to make.
This is raised from time to time. The policy is not going to change anytime soon, and is not open to debate. The site owner has heard all the arguments for and against, over and over and over.