Ugh. Okay, so let's see how this goes:
Guy with AS and comm problems -- and who knows that AS involves comm problems -- says he wants to engage in a major advocacy career. Woman looks at guy and knows this is not realistic, because a major advocacy career involves a lot of things the guy isn't doing or can't do: it's not just about being passionately interested in a subject.
I've been in the woman's shoes often. There are a few options:
1. Nod and pretend to take the guy seriously, and be blandly but nonspecifically supportive, then pat him on the back sympathetically when it doesn't happen. This works only if the guy doesn't turn into an inquisitor and demand you prove your faith in him. If you don't give him the answers he wants there -- this is all about shoring up his ego -- he'll decide you've betrayed him and have only pretended to have faith in him but have thought he's an idiot all along, and there goes all your hard work being blandly supportive.
2. Ask what steps he's taken to make this happen. At this point you become the focus for anger and bitter imprecations about how you don't understand how these things work and never you mind how he'll do it. You can have this conversation as often as you like, because the odds that he'll actually develop a plan and make it go are not good. Eventually he'll crumble and admit that he has no plan and that this is all a fantasy. However, you will be to blame for destroying his fantasy, and will have been revealed as a cruel person.
3. Point out that this is not a realistic plan and suggest an alternative. He will decide that this means you have no faith in him, despise him, and are a mean and cruel lady.
4. Be honestly delusional and throw in completely with his ideas. This will end in your impoverishment and the transformation of your living space into a [defunct reptile farm, defunct brewery, defunct gaming palace, you name it], but he will be persuaded that you, alone in the universe, believe in him, and so your next job will be to believe in his next scheme, which may involve his having to go to the Andes for six months while you stay here and try to sell off the reptiles and beer, but that's okay, isn't it?
I don't doubt, btw, that the woman really does feel she's not being heard. If that's the case and they're interested in staying together, she needs to learn much more about AS and modify her behavior, and he needs to go for the therapy, which may give him some relationship skills he hasn't got now.