Handicapped people should deserve to be treated better than anyone else.
Silence doesn't mean you have the rights to reprimand or make use of them if you feels like it. Helping you doesn't mean you have the rights to push all the blame to them.
It's a bad karma and retribution thing to ask them to do stuff that are beyond their limits and try to play them around like a fool. If they do.
They are people that could outstand us in their ability and capability which you could never forsee.