As long as we're on the subject of inappropriate reactions to disabilities, here's one that I've occasionally heard.

Many people of a certain religious sensibility commonly react to news of an ongoing or long-term tragedy by reassuring the unlucky party that "God only gives people what they can handle."

I know it a) is meant as a compliment, b) is the messy result of when the laudable desire to console meets the unconsolable, and c) may even be true on some level. But - coming from another person - it is also a selfish response: The person reacting thusly does so because he or she is unable to confront the reality without giving a reason, no matter how inapt. The "answer" may work for someone uninvolved with the situation on a daily basis, but here's a tip: it doesn't work so well for those who have to live with it. As such, it's about consoling the consoler.

Here are two responses I've (sort-of) bit my tongue on:

1) "Thanks for calculating our merits and deficiencies so carefully. Can we get a recount?"

2) "Suppose we want to have another child. According to the best current estimates, that child would have approximately a 1 in 15 chance of being autistic as well. So for the sake of that child, we should work hard to erode all of our coping habits and strategies, as well as undergoing hypnosis to forget everything we've learned about how to help an autisitic child. Oh yes - we should gamble away all of our money as well - it wouldn't be prudent to have any financial resources that could go towards helping an autistic child. Can't take the risk of actually being able to handle it."

It's much better to resist the impulse to answer the insoluble. Just expressing sympathy (and asking if there's anything you can do - with autism at least, the answer is usually "no," so it's a safe question) will encompass the overwhelming majority of what can be done.