> Should/do we allow foreign propaganda radio stations?

How do you define this? Is it foreign owned? Noncitizens are not guaranteed the same rights, especially citizens of hostile foreign powers.

> If we accept that the government can (and very much does) impose itself on content platforms for "national security"

Why should we accept this?

> what exactly is the difference between deliberately insidious information warfare, and collateral damage from market incentives?

None, both are concepts not found in the Constitution (if you’re talking about domestic speech by citizens) and both are protected by 1A.

I don’t care in the slightest about your fearmongering national security nonsense.