I would not say there was a golden age of political civility, since there always existed the practitioners of hate politics. But it used to be that people of differing political viewpoints sometimes did actually respect each other as people, rather than enemies who must be destroyed, and could see that sometimes people on other parts of the political spectrum had an idea that was worth considering. That seems to have disappeared from political discourse today, leaving hate politics to dominate any political discussions.
Related is the tendency to base opinions on an idea based not on the idea itself, but on who it is (most recently) associated with. There has always been such a tendency, but it has increased now.