I hate this argument, but here it goes: Google is a private company. Do they have a duty to the open web?
A bit more constructively: Who are the stakeholders here in the "open web"?
> show users rich content by stealing your website's traffic
Agreed. AMP allows ads, so when the users open the site the original site can receive ad revenue. But the snippets Google shows on the search results page likely deprive the original sites from traffic.
However ... it's not like Wikipedia wasn't already "stealing facts".
Why is AMP worse than Facebook's "instant articles", or whatever it is that the Apple news app does?
One reason Google wants the whole web to be "standard" is so they can scrape all information more easily, show users rich content by stealing your website's traffic, and create an internet information silo.