Sure, just as common carrier regulation is constitutionally valid. The Constitution isn't a suicide pact; the Founding Fathers very clearly did not intend it to be one. We've accepted a non-literal wording of the First and other amendments since the beginning.
> Why would the same logic not hold for restricting companies such as Twitter then?
Because being kicked off Twitter is hardly the same as not being able to dial 911 or purchase critical services. We've passed laws to correct specific, significant harms that are nothing like being unable to tweet. We weighed First Amendment rights against the rights of those being harmed in these situations and had to decide which conflicting rights mattered more.
That same process happens here. Different situation, different consequences, different decision.
> Spare me rebuttals of "if they really wanted to communicate, they could do so by carrier pigeon!" - 99% of users won't go through with such effort, or even know who they are being herded away from.
No need for a rebuttal. That's fine.