I think it made a huge impression on a lot of us because it speaks volumes about how you view interaction and how fundamentally different it is from the center of the bell curve.
That's fine; it would be boring as fuck if we all thought the same way. However, if someone has a history of comments that at least
come across as representing some kind of schizoaffective disorder, well, yes, people are going to take note of that.
Ignoring anything about relationships, gender roles, etc -- sexual intercourse is vastly different than masturbation along purely neurochemical lines because of the hormone release that happens from skin-to-skin contact, and other mechanisms. These are clearly evolutionarily rooted and there will be a lot of variance in it, but the experience you describe,
"Sex just feels like masturbating, using someone else's body"
is fundamentally extremely outside the mainstream world of human-to-human interaction. It might feel like that
to you, but that says more about you than it does about people who picked up on that comment and thought "lol, wtf, that's kinda fucked up".
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3115160/
He's made it real clear he has no interest in that, has tried it, and sees no value in it.
That's fine, that may be entirely true for him, it just means that his is genetically abnormal, because the drive towards sexual intercourse is one which has to be maintained for the species to survive. Conveniently, he takes himself out of the gene pool with this view, unless he is spending time donating to sperm banks.