Wait, what? You said Facebook is a monopoly, but just listed competitors in every single area Facebook is in.
Microsoft had (has?) a monopoly on the desktop OS (the only OS that mattered back then), before it diversified.
Google had (has?) a monopoly on search before it diversified.
Amazon has a monopoly on e-commerce, and is just now starting to really diversify.
Apple is the only exception-- they aren't really a "software" company though.
Claiming that Facebook should be broken up but not other big-tech companies isn't taking this into account.
Search is not Google's product.
It's hardly Big Company's fault that one non-employee X of Big Company forces another non-employee Y of Big Company to use something. It's X who is instigating it.