I would say that if someone cannot see the offensiveness in the words they CHOOSE to use, then they are lacking in empathy, it doesn't make the word less offensive. Also, when the words they CHOOSE to use are clearly meant to offend, then it's not a matter of anyone choosing to be offended, they are merely picking up on the offense the speaker means to convey. Another example, calling someone's mother a "fat lump" is clearly offensive when the intent of the speaker is, precisely, to offend.