Any fallacies here?

Oh, good god, no. Private businesses are subject to municipal and state law, and therefore subject to their laws. In a global pandemic, these laws can be changed and legally enforced. Twitter may be a privately-owned social media site, but there is zero person-to-person contact. They are entitled to restrict or even expel those who do not comply with their community standards. Private clubs are permitted to require dress codes, etc. In some instances, they are even allowed to restrict membership with the proviso they do not discriminate against creed, color, religion, or gender. Some do, but they can be legally sued. Then, it's a matter of law, not logic.

I'm going to address the charge of censorship rather than that of dictatorship which Dr. Bo has more than adequately debunked.

It's hard to ignore the underlying Tu Quoque (ad hominem) "Whataboutism" implied in the claim. What to speak of a glaring false equivalence that deceptively conflates Trump's openly and well-established effort to suppress information, nullify The Media's influence, and punish anyone who contradicts his barrage of lies, subterfuge, and disinformation.  All forms of censorship in its bald attempt to claim the truth exclusively for himself and his propagandists. All tax-payer funded employees with very different legal and constitutional restraints.   ( The Logan Act, Abuse of Power, etc.)

The possible equivocation problem is that it shifts the charge of censorship from a publicly elected government official to that of a private organization. This is a false equivalence. Twitter is not a publicly tax-funded organization, but a private organization with its own standards of community rules and legally sanctioned discretionary by-laws. 

If a private establishment imposes a  No shirt, No shoes, No Service policy it is not an infringement of First Amendment Rights, whereas if the federal government imposed such a rule on the citizenry it would be on very shaky constitutional grounds.