Cougar, would you have a go at justifying the 'obvious' choices of banned words as above?
I've tried to explain several times now as I understand it and you're (probably wilfully) not getting it.
I won't - and indeed, I can't - "justify" anything as I don't make the rules and have no control over the blacklist. If you want justification or object to the policy then you need to take that up with the site owners. Though if it were down to me I wouldn't change much as it seems to work well.
My take is that profanity is blocked in order to keep the site vaguely respectable / family friendly, but that does not extend to censorship of views and discussion (and IMHO rightly so). A free-for-all on swearing would give a very different 'feel' to the forum; would you want your 14-year old daughter to sign up to Mumsnet?
Directly offensive comments (eg, calling someone a chink as opposed to debating whether referring to a "chinky" take-away is racist or not) is similarly forbidden. Would we gain anything by adding "chink" to the swear filter? I doubt it, we'd just repeatedly hit the Scunthorpe problem.
I could be totally wrong here but it's the best I've got.