"Free" doesn't mean no restrictions. For example, apps/websites like Myspace and Facebook and anything that's been used to spread hate, cause bullying, or threats have always been a target of regulation, albeit never an outright ban.
In the case here, it's ostensibly being done with national security considerations in mind. What remains to be determined is whether or not these concerns are valid. But the idea that "free" means the government has no power to ban things, including apps, borders naïvety.
I think you totally missed the argument: it's not about copying anything China does, it's about reciprocating restrictions that they place on your country. If China places a tariff on US imported goods, then the US places a tariff on Chinese goods.
This is and has been the case even for non-adversary countries, and is bread-and-butter foreign policy
Reciprocating tariffs has been a thing for hundreds of years before the US even existed. The justification isn't "they're doing it, so let's just copy them", it's "they're inflicting economic impact on us by reducing the profit of our exports to them, we'll put pressure on them to stop that by reducing the amount that we import for them".
It's not simple "but he hit me first" logic: it's macroeconomics with an actual strategy in mind.
I would definitely be more okay with allowing Chinese websites/apps in the US if China wasn't banning so many Western ones: https://en.m.wikipedia.org/wiki/List_of_websites_blocked_in_...