There is certainly an argument to be made against arbitrary removals of content. I agree that perhaps there should be limits on networks above a certain size. However, Twitter banning Trump was anything but arbitrary. The fact that they didn't ban him sooner despite his frequent violations of their TOS is evidence that they were biased in his favor, if anything.

Sure he was "sitting president" but he was actually stoking flames of violence the day he got banned.

In general Twitter was a terrible enabler for Trump, he's such a coward that he didn't dare firing people face to face, he fired people with tweets. And it made him a keyboard hero conveniently attacking people using it, if he had to go in front of the press to spout his bullshit he surely would've been more reserved, because there'd be direct pushback for everything he said.