It boils down to the First Amendment, the government cannot censor speech. In US law groups have the same free speech rights as individuals. Michael Moore doesn’t lose his free speech rights when he makes a propaganda movie with a film studio, and Citizens United didn’t lose their free speech rights when they made their propaganda movie either.

Citizens United wasn't the decision equating money with speech. I don't know offhand which that was, but it was much earlier.

IIRC, Citizens United was the decision that allowed much more and much more opaque spending on political campaigns by corporations and wealthy individuals—it allowed the creation of SuperPACs, for instance.

I am not making any reference to Citizens United. This started in the US in 1981 and there was FDA guidance issued in '85. "The FDA said in 1985 that drug makers could air ads, but they also had to follow rigid rules for disclosing side effects and other information." [1]

1: https://www.statnews.com/2015/12/11/untold-story-tvs-first-p...