Earlier quoted context omitted.
Their choices are to either be GDPR-complient, or to completely bar all EU users from accessing Facebook. They cannot use tracking opt-in as a requirement for access.
American here; I just don't quite understand the premise. "Here is what you are giving us, and here is what you're getting in return" seems perfectly legit to me. If this interpretation of the law is correct, then the government is essentially saying the "in return" portion has to be eliminated. Which seems to be against the idea of trade.
In the specific case of Facebook, near-zero of the users actually understand either what they are giving or the full extent of what they are getting or not (especially since the latter changes constantly as FB alters their policies and algorithms etc). So, it's more like "give us stuff you don't understand with ramifications you haven't thought about, and you get a complex, somewhat unpredictable, changing service." This is nothing like the theoretical trade between two participants with equal power and complete information.