A Flat face = "retarded"?!?!?!

This has been nagging at me for awhile, so I need to vent. SuperGrammy's sister recently told her that because Monkey Child has a flat face that he is likely to be "retarded".
First of all, this thinking and assumption is based on ignorance and stupidity. The shape of one's face does not dictate mental retardation (eye shape and other particular features can be indicators, but not just having a flat face). and calling someone "retarded" is very outdated. It's "developmentally disabled".
Second, he underwent genetic testing when he was born because of the spina bifida, and that was one of the first things he was screened for! and he came back with a normal chromosomal mapping with no trisomies or anything.
Third, she did not have the balls to say this to our faces, but told my mother in law, who quickly defended our son and told us when it happened.
Lastly, why would it matter if he was developmentally disabled? He's still a sweet, lovable child, and is deserving of love.
This is the same aunt that, when we announced we were pregnant after seven years of trying, shouted "Finally! It's about time!" While I try not to take anything this woman says with a grain of salt, this just pissed me off. She's not the brightest bulb in the sign, and even her daughters admit she has some serious mental issues that require commitment to a psych ward but she will never get the help she needs, but this....this was the last straw. We told SuperGrammy that from now on we would prefer that she not take Monkey Child to her sister's house, and that if that becomes an issue to please let us know and we would make other arrangements for child care, and she agrees to that completely. I am hoping that we do not have to see or deal with this woman ever, but since she lives in the area it might not be possible to avoid her. We do plan on boycotting any family events involving her, and Bald Man's dad would not go if we don't go, which means a lot.

GRRR!!!! How can ignorance like that be combated if the person who is ignorant is unwilling to listen to reason, logic, and scientific proof????