I'll admit the use of 'unilateral' here is probably poor, I don't know the proper one. These companies exert monopoly power in the markets they are in. Decisions made by companies which are monopolies are "unilateral-ist" because once a small number of them make a decision together (perhaps colluding) then it leaves no recourse for the person or group they are deciding against.

Mentioned elsewhere, the process we should all wants is one where if a company wants to nuke an entire speech platform like this due to illegal speech, they can get a judge to affirm the legality of the content and the negligence of those who are hosting it. With that in hand, their actions would be immune from criticism. Without it, we find ourselves here, where we basically have to trust them to make the right decision and not abuse their power. It's not what we should want, for the same reason that we should have wanted anti-trust laws in place to reduce the power of monopolists, despite the fact that monopolists were operating entirely legally and often ethically.