I think you are dead wrong. The only political debate prior to talk radio was absolutely one-sided. All "facts" were controlled by the MSM and any dissent was virtually killed by the "fairness doctrine."
The rise of talk radio has hurt the left more than anything, and the left has actually degraded the quality of political debate as you say. They are the ones that cannot respond to the truth when it is presented by people like Rush.
In the old days, even small towns had two newspapers with competing political views. Large cities had five or six.
I miss the old days.