How does that make this okay? Nobody is entitled to get a company’s services for free just because you think their price is too high or their front ends aren’t built to your liking.
Google specifically does not publish their API for free consumption by other companies, yet that’s what’s happening here anyway. The company is also using specific tricks to circumvent detection of the behavior.
In your analogy, this would be like a crawler ignoring robots.txt and then scraping the content for their own website with zero attribution to the source, which is nothing like Google indexing your site with full attribution and driving traffic to it for you.
Regardless, “turnabout is fair play” is unequivocally not a legally or even ethically acceptable standard, so that argument wouldn’t actually hold up anywhere anyway.
Google ignores the noindex directive in robots.txt now. You're supposed to put it in your HTTP response headers or HTML meta tags...
https://developers.google.com/search/blog/2019/07/a-note-on-...
I did mention rich snippets.