:: ANOTHER SIGNIFICANT TEST (known as vertical/horizontal relationship, if I recall) ::
The horizontal aspect is communication among themselves regarding business plans/technology improvements. The vertical aspect is The Cloud, to which they are all connected and interact with using algorithms and bot-crawlers.
Great insight ... but I think the Sherman Act of 1890 preceded the cloud.
Anyway, in this context horizontal means “Competitor” and vertical means “Supplier.”
Under certain conditions it is illegal for a supplier—especially one uniquely situated due to market structure (e.g., Google, Twitter, YouTube or FB) to use that position as a supplier to disadvantage or hinder a competitor who is also a customer.
I think downgrading their access, or banning them, constitutes such unlawful interference. The fact that, as Q points out, they are all acting in concert, using a similar pattern to attack the same individuals and companies, makes this a CONSPIRACY.
Q: Break up BIG TECH.