I too grew up without free speech in a dictatorship and believe fervently in free speech. However I believe too that dictating to a company what speech they can have or can't have on their platform is a violation of free speech in itself. It is their right to disagree with someone's opinion and to deny them access to their platform. If we disagree with that action we punish with our eyeballs, or our wallets or we build our own.
That these platforms are so huge is a problem for sure but doesn't automatically classify them as institutions owned by the public. There are other ways to deal with companies that get too big.