Well, I have a lighter but somewhat similar story. I deactivated my FB account a good 4-ish months ago. I went back to change my name (to indicate for folks where to find me) 2 weeks ago and I was greeted with a message that I cannot post or comment for 60 days because one of my posts (they showed which) is against community guidelines. I posted that a long time ago (8+ months) and it was fine until it apparently wasn't. The post was a single image, this one: https://imgur.com/a/BqgX28c

Without specifics, Facebook has basically given the suspended person freedom to choose whatever reason they want. This is fair.

If Facebook doesn’t like this explanation and it circulates to millions of people, they are free to offer a competing explanation.

Arguing an unproven point isn’t a problem here, it’s a strategy, and it’s a good one.

A good guess for the actual reason would perhaps be that someone who posts lots of links runs a risk of posting ones found in a blacklist. That blacklist probably doesn’t deliberately contain “competing social networks” though, but could contain such links in error, indicated as phishing or malware.

Most likely.

However, given the strength of Facebook's monopoly, they have the power of a state over people's lives (e.g. via a livelihood that depends on a Facebook account).

The lack of due process (https://en.wikipedia.org/wiki/Due_process) is very worrying.

The Magna Carta says "No free man shall be seized or imprisoned, or stripped of his rights or possessions, or outlawed or exiled, or deprived of his standing in any other way, nor will we proceed with force against him, or send others to do so, except by the lawful judgment of his equals or by the law of the land."

This feels like a breach of that, even though it is a monopoly corporation, instead of a state.

It’s still facebooks fault for not providing a real reason. They should show the reason a user got banned and not just a vague “rules violation”.