Ah, +1 informative, thanks. But when you call someone retarded, jokingly or otherwise, you’re saying the person’s mental development is stunted. When you call someone a spaz you’re not saying they have a type of cerebral palsy, and you would never call someone with c.p. (or an epileptic, etc.) a spaz. (Again, this is in U.S. usage.) I don’t know why it became so much more offensive in the U.K., while they go around calling everyone “cunts” and no one seems to bat an eye.
