Large privately-owned platforms carry so much discourse across today's society, that censorship and deplatforming in those spaces has the same impact as governmental censorship, for most intents and purposes. Even if these corporations do not constitute what we might traditionally call a "monopoly", they control a large-enough share of traffic to have significant impact when they take artificial actions. That sizable impact is exactly why they are being targeted (not just on this topic but others) by activists or other agents pushing for deplatforming/censorship favorable to their causes.
The big risk is this: when only a few entities funnel so much societal discourse or control our communication infrastructure or process payments, those entities making arbitrary decisions about who they serve has similar impacts/risks to the government imposing similar restrictions through the law. These companies should not act as a thought police and should not impose their own personal governance above what is minimally required by the law. Nor should they rely on the judgment of an angry mob to make decisions.
"The same impact as governmental censorship, for most intents and purposes." False and dangerous. Government censorship means imprisonment and other forms of punishment, sometimes including death.
This doesn't mean your point is wrong (I don't think it is), but it's more effective to make your argument on its own merits rather than making a false equivalency.
The big risk is this: when only a few entities funnel so much societal discourse or control our communication infrastructure or process payments, those entities making arbitrary decisions about who they serve has similar impacts/risks to the government imposing similar restrictions through the law. These companies should not act as a thought police and should not impose their own personal governance above what is minimally required by the law. Nor should they rely on the judgment of an angry mob to make decisions.