Forget when or where I read it, but during some net-squabble or other about some damn thing (I was not involved personally, you understand) this phrase appeared: "the brits are all limeys anyway." I sat there and blinked a few times, trying to work out what they were on about. Yeah, the brits are limeys, the sofa's a couch, the telly's a TV, football is soccer, what's your point? Then I realised: Being called a limey is supposed to hurt my feelings.
Sorry, but, uhhh... before you decided to wield that mighty implement of emotional pain, did you pause to consider the fires in which it was forged? "Limey" was the nickname given to British sailors in Captain Cook's time because they, erm, ate citrus fruit. You know, for the vitamin C. To prevent scurvy, yes? I think you'll agree that as cultural/ethinc slurs go, "You don't have a life threatening vitamin deficiency! You've got most of your teeth! And no weeping sores to speak of!" lacks something.