The rules for US broadcasters on "controversial matters" have been changed a few times and in two separate areas.
One is the Fairness Doctrine which is what I think you refer to, and that was ditched in the Reagan era, although the FCC didn't kill the rule in the Federal Register until sometime during Obama's first term. It was about a public service requirement for news broadcasts to air info on controversial matters and to present them in a "fair, honest and equitable" manner, although it didn't say how that had to be done, i.e. as news, editorializing or some other format like a panel.
The other is
the "equal time" rule, dealing with political matters and it has been messed with endlessly on a case by case basis over the years. Of course it has got entangled with money: providing time for a political viewpoint aired in a commercial at the same monetary rate as for a favored sponsor. There are exceptions to the rule: "documentary,
bona fide news interview, scheduled newscast, or an on-the-spot news event". And predictably some of those land in court.
The whole subject is the land of milk and honey for lawyers, and why not, since it bears directly on the First Amendment.