The article's point is that though we generally rank autistic people as retarded according to intelligence tests, these tests are biased towards a certain form of communication. If the autistic people communicate on their own terms, they are often quite bright. There is an intelligence test called Raven that can get past the communication barrier better than the standard test.

And, at the risk of being pedantic, there are multiple levels of irony going on in my original response, since the subject is misunderstood communication.