Using the term "Autistic" as a term of political abuse is about as low as one can get.
Great quote in this piece from BBC online from the Lib Dems Norman Lamb MP who said: "This may have been a casual off-the-cuff remark from George Osborne, but that doesn't stop it being offensive. Opposition politicians have reason enough to criticise the Chancellor without having to descend to these ill-informed comments. This won't do much to help the attempts to portray the Conservatives as a caring, sharing, modern party."
Well said Norman. As for George Osborne instead of trying to wriggle out of it like a naughty schoolboy he should apologise - simple as that