It's not. This whole thing is a giant misunderstanding based - as far as I can tell - on a single RAT in Congress doing an Alec Baldwin-style bloviation, claiming that "repealing the FCC ownership limit changes is just the first step, and next we're going to make the Fairness Doctrine into federal law!"
Regardless of what your opinion is on the FCC rollback of the station ownership limits (which wasn't even that much of a rollback), it has nothing to do with the long-dead Fairness Doctrine. In addition, the Supreme Court made is crystal clear 20 years ago that the Fairness Doctrine was only constitutional as long as the dissemination of news and opinion was largely controlled by federally-licensed radio and TV stations, and that the moment technology took away that monopoly, the FC would be ruled unconstitutional. That's why the FCC repealed the FC just a year or so later, based only on the fact that cable TV was starting to gain ground. Since then, the number of cable channels has EXPLODED, the number of broadcast radio and TV stations has EXPLODED, we have two more news channels, the Internet, the web ... we now live in a world where anyone with an opinion can put it out there for the entire rest of the world to see.
So even if the single RAT wasn't a blowhard loser, and the FC was passed (and Bush signed it, an even more laughable concept), an injunction would be issued against it the same day, and a few months later the SCOTUS would nuke it.
There is NO threat to talk radio.