Over here if you call some a fag you are inferring they're homosexual. In the UK, you'd be calling them a cigarette. Calling someone a cracker in the US is a derogatory term.
"Retarded" used to be an acceptable word, until people decided it was "derogatory". Then they said you should use "special" instead, until that became "offensive". Then they went with "mental disability" and "mentally challenged" and also "mentally impaired", which people again took offense at. Today I see they want to use "developmental delay", which is of course offensive. My point? People can either stop being insensitive or stop being so sensitive, but neither is going to happen. Why? Because people are retarded, cracka!