Many users don't know what AMP is, and don't really care—in fact, there's some evidence that users like AMP in search results, or at least they like the performance—but as far as I can see in tech communities like HN and Reddit, the vast majority of people who know what AMP is also know that they hate AMP. (Scroll up and down on this thread a bit!)
As for why it's toxic, I don't think we have to agree about that, but it's not just the UI problem. The URL problem (AMP URLs point to google.com instead of the original site) is a real, significant problem in its own right.
The URL problem is the root of the claim that "AMP is Google's attempt to take over the open web."
IMO, if it were just an iOS scrolling issue, AMP would just be controversial: love the speed, hate the scrolling, eh, it's a wash. But the URL problem is what really gets the flamethrowers running!