That's pretty rude and extreme. As a recent parent, I keep an eye on the "autism epidemic" because that scares the crap out of me. But Denis Leary has always sought controversy; I haven't listened to him in a while, but I like his earlier stuff, and downright admired him for his early MTV appearance when he said, "I've got three words for Al Sharpton: Martin Luther King." To say that on MTV in the late 80s was pretty brave...
For a look at the other side of the coin, I don't think he's referring to the truly autistic. I don't know what the cause of the growth in autism is, but I think he's referring to the borderline cases (Asperger's Syndrome, etc) who were raised on TV and the Internet in an otherwise empty house by parents who've replaced parenting with things. "Daddy's got to go screw his secretary at a conference, and Mommy needs her 'me time' with the masseur, so here's a new video game!"
It's like the antisocial side of ADHD... Schools are pressured to "do something" when the parents aren't, well, parenting. "I can't be a bad parent; there must be something wrong with my kid!"