You're ignoring the fact that "Facebook dot com" isn't just used by those with a Facebook account; it is also used by Facebook-the-company and its customers (ad

You're ignoring the fact that "Facebook dot com" isn't just used by those with a Facebook account; it is also used by Facebook-the-company and its customers (advertisers, propagandists, etc.) against those with a Facebook account (in order to extract revenue). This leads to things like "optimising for engagement", and outrage turns out to be highly engaging and easy to produce.