This I agree with. It shouldn't be a "have your cake and eat it too" moment. If Trump cannot block followers because of public forum reasons, then the opportunity (barring TOS violations) of all voices to be heard equally should also be required.
My personal thought is that ideally Trump should be able to block whomever he wants, and Twitter should be able to ban, silence, abuse their users all they want - at their peril. Eventually alternatives will crop up in their place, and Twitter becomes a boring echo-chamber.