It's the one line we don't cross. It's fairly well established and it's unnecessary. If you want to be racist there are sites on the web that cater especially for you.
I personally don't care, it's just kind of funny to see a site where it's no holds barred all the time. And then suddenly someone brings up racist jokes (not even maliciously being racial) and people are worrying about having their feelings hurt.
Have to admit it's amusing