Devoreal
The CEO of Parler can go out and buy the same servers that Amazon, Google, and Apple use and set up their own system.
Additionally they can also refuse to host ANY content by Apple, Google and Amazon.
So there are no violations if Parler can still go out and set up their own service. They will just have to use equipment that they (PARLER) owns and use the tech services of their own employees.
A Hunch
Antitrust violations = no
Censorship violations = yes.
Anonymous
No. Their site their rules.
Remember the wedding cake?
You can't have your cake and it it too.