[alkonaut]

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.