Okay, first, autism is in the DSM. It's just as much a mental illness as bipolar disorder, schizophrenia, or any other thing in the DSM.
And to be clear, as with literally any other mental illness in the DSM, you can be affected by it to different degrees. The autism banner isn't just the people who struggle with social cues. It covers everything from that to people who are non-verbal and can't leave their house by themselves.
All that said, it feels to me like you're drawing the lines in the sand where they make you feel good, not where they make objective sense.
It feels like you're saying that we shouldn't hold autistic people accountable for being a particular type of asshole because they "just can't understand." That's dehumanizing my guy. I know a lot of autistic people. The vast majority of them have learned good social etiquette. Is it harder for them? Sure. Are they always perfect? No. But they recognize that to be a good member of society they'll have to work harder in some areas to overcome certain things.
It's not about hating a blind person because they can't see. It's about hating a blind person for repeatedly and unapologetically kicking you in the shins. The solution to reduced capacity isn't to ignore and excuse it. It's to be understanding and patient as they do the work to overcome it.
There are plenty of people with narcissism or schizophrenia who are excellent, fully functioning members of society who are just as good of people as you or I. Who love their friends and neighbors and don't lean on their condition as an excuse for their behavior. Is it a god-aweful amount of work and introspection to do so? Absolutely. Is it easy? Absolutely not. But they have agency the same as you or me. The same as someone with autism. But some people choose to overcome. Some choose to embrace the treatments and therapies needed to allow them to be a good neighbor and friend and citizen. And they have the agency to do so.
I do think it depends on where you live. In about half of states, your vote for president is meaningless. Mississippi isn't going blue and Massachusetts isn't going red. In those cases, voting third party has the chance to effect future federal election funding.
But yeah, if you're in a state with literally any chance at all of being a toss up, don't vote 3rd party.