MacFarlane: "You're not going to call a person with a mental challenge retarded, you're just not going to do that, we don't we that's not what that's...no one with any sense uses that term in that way."
Gotta love the double standards here. The real-life down syndrome girl might have thought the joke was funny but can't understand why specifically targeting the joke towards another real person might cause a stink.
How about I go tell a few dead baby jokes to someone who lost their kid in childbirth. I'm sure they won't mind if I point out it isn't about their kid right?