In his bit on soft language, Geore Carlin's says cripple is a perfectly dignified word. I agree with him. The thing is you did not use "retarded" in a dignified way. Ghetto is a perfectly fine word. Do you see why saying "This jam has no theme becasue themes are ghetto." would be a problem?
I am genuinely asking. I truly want to know. Why is this so important to you?