Linguistic Confusion: Private vs Public Property
All companies want to be monopolies. If you get rid of the competition regulator run by the government then sooner or later some company or a group of companies will start crushing its competitors. At that point, they can start dictating the rules of commerce.
This means that all companies are essentially proto-governments that are kept down by a monopolistic competitor. This competitor is what we call the government. Modern governments are predominantly estate monopolies.
That there is no practical difference between a government and a monopolistic company can be seen by thinking about the difference between a private Mars colony and a Mars government. Both have laws and people who enforce those laws.
The relationship between a government and a company is the same as the relationship between an app store and the third-party companies that use this infrastructure to market their apps. The former controls the estate and keeps the latter from undermining its monopolistic power.
The problem with proto-governments, i.e. companies, and the reason why we want to keep them down is that they are essentially dictatorships with arbitrary justice. Their terms of service and internal power structure did not yet face the selection pressure that formed modern constitutional states. The latter feature many safeguards for customers. Constitutional states give customers legal certainty, equality before the law, the ability to appeal verdicts, and to remove those who design the terms of service, i.e. the laws.
Preferring companies to make decisions about civil rights rather than governments, therefore, means preferring unaccountable dictatorship over constitutional democracy.
P.S.
One doesn't even have to invoke network effects, an asteroid mining company with a first-mover advantage making use of kinetic orbital bombardment, or runaway artificial intelligence to see that a free market cannot possibly prevent the rise of monopolistic entities.
If you believe that monopolies and cartels cannot arise in a truly free market, ask yourself how a completely free market would prevent the creation of a government. Governments naturally emerged out of anarchism.
Anarchism can only ever be a transient phenomenon. People demand security. If you get rid of the police then people will form militias. The same is true for libertarianism.