By this logic, would not Facebook and it's market leadership in social media be a better target?

Not that antitrust has to be based on market share but - it is kinda hard to claim Facebook has a monopoly on much of anything. Facebook is a big player but there are dozens of big alternatives. That is not at all the case for Google. Search, YouTube, browsers, Android all have a dominant market position.

Fair, but, conversely, Facebook has a well documented history of growth through acquiring or cloning competitors.

Better? No. Equally valid? Certainly.

Wait until I tell you about the major media corps!

Sounds rather Staliniesque given his infamous quote about not allowing enemies pens.