It's really not how Apple would treat any other company. Any other company would get banned from the app store permanently.
I do agree that this is measured. The question is how long, if ever, before Apple grants them a new cert. If Apple lets them back into the Enterprise Developer Program, this is a few days of inconvenience. If they keep them out, this effectively kills their apps on the iOS app store because FB can't effectively work on the apps internally.
I imagine this is how apple would treat any company with a widely used app. Whether it was Snapchat, dropbox or Candy Crush Saga. I doubt they'll consider such a misstep reason enough to inconvenience or even harm millions of their users.
It does not preclude test flight or just installing it through a developer machine. The vast majority of app developers don't use an enterprise account to test beta releases.
Facebook's development process for iOS (and android) is dependent on having most/all employees dogfood beta releases and report bugs that can be ignored. This breaks that pretty badly, and now users in the wild will have to report bugs before they can be ignored.
I hope they'll drag it on indefinitely, and maybe the two will have a giant war of sorts. This is one of those cases where I don't like either side, so I'm happy to see them having a destructive fight.
I do agree that this is measured. The question is how long, if ever, before Apple grants them a new cert. If Apple lets them back into the Enterprise Developer Program, this is a few days of inconvenience. If they keep them out, this effectively kills their apps on the iOS app store because FB can't effectively work on the apps internally.