As best as I can figure out, from what I saw, was the media shifted to the right when Reagan got elected. They slowing began purging the liberals, claiming a shift in America to the right. There was no real shift, it was manufactured, but they then stacked the airwaves, morning, noon and night, with right wing wackos. I can remember at one point when you would turn on the radio and it would be G. Gordon Liddy followed by Oliver North and so forth. Twenty four hours of the right wing.
Did you see how they did away with free form radio and I remember when the top 40 station in NYC, WABC, went to all talk.
That means that kids growing up in the 80's and 90's had nothing else to listen to and watch but the Right Wing Media, and it was labled "Liberal Media," but it wasn't and still isn't liberal. Of course they have a few token liberals scattered here and there so it's not so obvious but plenty of right wing and wishy washy centerists that are called liberals. These centerists are always weak, indecisive and usually have little facts and say things like "But it's wrong." We are also saturated with cop programs and movies that always show the cops to be right and usually have to "break the law " to catch the bad guy. They are usually victims of Liberal courts. It's to condition society for the police state.
I followed the alternative press since the 70's and began reading the Nation and the Progressive in the 80's so I always got the truth. I saw how the corporate media was lying then but it still had some good investigative and independent minded journalists that exposed good stories and the whole media took the credit.