It's not even content per se, it's much more insidious than that.
The comment I originally replied to likened tiktok to a printing press, but that's not quite right.
Imagine a printing press owned by an enemy that would subtly manipulate the text of whatever you tried to print. Or maybe it would omit entire articles from certain recipients of the newspaper, or reorganize the page layout to emphasize different things than the editor intended.
We wouldn't allow this hypothetical printing press controlled by a hostile foreign government to be sold in the US, we would be crazy to.
Actually, yes, we would allow such a thing. Plenty of our news organizations are foreign – owned, and many of them are very elegant to your hypothetical printing press. The US simply doesn’t have the constitutional or legal framework to regulate content reproduction for ideological reasons.
The content is not what is being outlawed, only the distribution mechanism. ISIS wouldn't be allowed to own a publishing company in America; nobody thinks that somehow curtails freedom of speech. If somebody so chooses, they could distribute content from ISIS, and restrictions on that would indeed be a restriction on speech. But it wouldn't be a restriction to make it illegal to give money to ISIS.
So if you want to make the same argument, you will have to declare china's CCP to be a terrorist organization - and all of the legal implications that entails.
That's not a constitutional requirement. There's no law that says the government can only do this to terrorists. In fact, even if somebody is a terrorist, if they're American, it would still be unconstitutional to deprive their freedom of speech. ByteDance, as a foreign entity, enjoys no such protection.