I think the worst disability would be being paralyzed from the neck down, deafblind and mute all at the same time - now talk about being locked in!
But I agree with Chase and the rest of you. Choosing to embrace that ignorance as fact with out even bothering to do some REAL research is the worst because that person believes in the stereotypes to the point that they see only the things the other person CAN'T do rather than what the CAN do. It is sad!