A private, for-profit social media service can decide which customers they want business from and which customers they don't want business from. It's one of the main rights you have as the operator of a business: the right to refuse service.

The conspiracy theorist's right to free speech doesn't mean Twitter is obligated to carry their speech, either.

If you dislike this your best available remedies are 1) find a service who wants your business, or if none such exists, 2) start your own social media service, or to "solve" the problem for good, 3) engineer the existence of government-operated social media services such that law mandates all citizens have unfettered free speech on the service