World is a really messy place. It's not very easy generally to decided if in a political conflict one or other party has moral high ground. For instance we have several Nobel peace price winners now participating in plausible genocide (Aung Sang Suu Kyi and Abiy Ahmed). Who has the moral high ground? I have no frigging idea, but I don't think an unelected corporation should decide either.
If Twitter takes the side Trump is a crook and should be perma-banned, this creates a precedent for silencing the voices of opposition voices around the globe.
Edit: I mean in the context if Twitter is designed to be a fair medium for anyone to express themselves. Of course it does not have to be like that and can block anyone without infringing anyones rights as such.