There are multiple, billion dollar companies where users rent out large, personal assets to others. I don't see that as "nothing to support the idea". It's direct evidence that people are willing to do it at a reasonable level of scale.
I'm not sure what level of scale you're thinking or what you're responding to at this point. If you can scale back a bit on the hyperbole and adversarial mindset, I'm interested to discuss.
However I do think that % of people will be higher than it is today because full autonomy creates more situations where you've bought an expensive asset which sits idle throughout most of the day when you're working or sleeping.
Elon's assuming that Tesla will be the first to market with Level 5 autonomy. If that's the case, people will be willing to pay a huge premium to get one, especially if they think they can offset the costs by having it "pay for itself while you sleep".