Re: Um, this is ridiculously illegal
Um, you have no idea what you are talking about. Were they saying, "you must have autism to work here" then they would be in trouble, but they are not doing that. They are not requesting any potential hires to state their disability; they are opening additional, optional interview paths that might be less biased against disabled. Autistic people are welcome to go through the standard hiring procedures and not mention their disability. It's not like existence of a wheelchair ramp forbids you from struggling up the stairs if that's what you really want to do.
Also, everyone knows that autistic people are not all genius, and you are either being disingenuous (or stupid?) to imply that Microsoft is not aware of this. They are merely broadening their hiring pool by removing some of the arbitrary, and therefore ultimately inefficient, ways that potentially useful hires are eliminated by routine interview procedures.