We did used to have FCC rules that largely prevented the problem without any Ministry of Truth, but the rules were abandoned because billionaires found them inconvenient.
The Fairness Doctrine? That might do it. If people who only get their information from one source get both sides from that source, that might help.
But I suspect that these days, there'd be just a caricature/strawman of the other side, not an honest presentation, and therefore it wouldn't actually help. (And I don't just mean Fox would do it. I could see CNN doing the same, just less blatantly.)
And, those who only want to hear one side can get their "news" online these days. So I don't think it would work. It might help, though.
