Doesn't matter what the TOS says. They are destroying their brand. Last week I had some trust, now I have less. Next week I may have none. I can say that I am already looking for alternatives.
You are destroying your brand. I know literally dozens of people that have enthusiastically come over from FB who are deeply freaked out about what you are doing here.
Yes, you can remove someone from your service if you like. But you must let them retrieve their materials. Otherwise, please trust us: We will go somewhere else. Behavior like this from FB is why we came here in the first place.