The FCC exists (in part) to enforce a certain morality on public broadcasters. Whatever we think about that today, that was a core responsibility of the FCC when it started and that still exists today.
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Whatever you think it did, it almost certainly did not do that. In practice it meant that J. Random Crazypants would be allowed to give an editorial -- sometimes in the middle of the night, and sometimes as 60 second after the news. Additionally the Doctrine never applied to Cable TV for obvious First Amendment reasons.