The inbalance comes where 80% of the journalists subscribed to one set of opinions. This, because journalism schools are equally inbalanced. Liberals are drawn to education in a way that conservatives are not, in part because they hold to the dogma of the perfectibility of man thru education.
80% of journalists subscribe to one set of opinions because 80% of the people hiring those journalists subscribe to the same set of opinions.
Prior to 1960 the media was predominately conservative, probably for the same reason. I’m not saying either was wrong but the outcome was. America can only survive with a balanced information dissemination system.