It isn't your business and if they're able enough to get into consensual sexual experiences then the level of autism isn't at the rate where it's unethical.
Someone with the social capabilities of a child is a different matter. I feel pretty young so I'm very picky about my experiences because I've been groomed before, as an adult.
(If they're able to navigate the social world of adoption or sperm donation/surrogacy, again, I wouldn't worry).
I had two aspie parents growing up. Unusually, I had three parents. A stepdad who adopted me, a mother and a father. My father shouldn't have had kids I think. He's schizophrenic and paranoid and has meltdowns regularly where he shouts at people. He doesn't care if kids are about. I had to put up with that all my childhood, and the risk of violence. At some points, I suspect he really was violent and that mum's lying about it because otherwise I had very vivid dreams of it.
I suppose meltdowns might look like this in some autistic people, those people specifically should consider those risks when having kids.
My stepdad was a different matter. He's a stubborn old sod. Sometimes he can be a social burden, such as when he's brutally honest to people we don't know well. But he's clever and creative and allowed me an imaginative childhood with room for learning that I suspect a lot of NT parents wouldn't have allowed. My mother allowed/encouraged it but I think that's because she's a lot nicer than a lot of other NTs. My happiness was the main focus of her life.
If I were to ever have kids (outside my paracosm) I would want to have kids who were the sort formally known as aspie. I would bear the meltdowns for the sake of intelligent children who saw things their own way and weren't as socially influenced. I would help them through the bullying and the sensory issues. Maybe this is because I haven't seen anyone with severe autism.
I know I'm not being PC here. I know you're meant to act like everyone ought to feel able to/be allowed to have kids. I'm glad of my own existence but honestly, I wish my biological father was someone else. And I'm saying that as someone who loves him in spite of the horrible experiences I had as a kid - but who keeps him at a distance for safety's sake.
And if someone isn't capable of consenting properly then them having any sort of sexual experience or entering into social contracts about taking care of another human being (it would be stopped so unless you're in a culture where adoption lacks structure and a vetting procedure, I wouldn't worry. Mum wanted to foster a kid and they went into every aspect of my childhood, her childhood, my stepdad's childhood, our current life, life in the area etc. This is for a kid who lives at home in the week and it isn't a long term thing. Adoption I imagine is stricter) ... is something to concern oneself about.
I think if they're aspie they'll have considered things like the endless noise a baby emits and whether they're not too sound sensitive for such things and the need for a new routine when baby comes.
But in general I think that aspie parents make for nicer ones for the kid to have than a lot of horror stories I've read about some, even law abiding/relatively decent, NT parents. I couldn't have wished for a nicer childhood from the ages of 9 to 13. It was unusual, for sure. But I think a lot of childhoods are.