Throughout the history of politics, the discourse has been rancorous. If your parents did not tell you never to discuss religion or politics in polite company, you learned that lesson on your own. 'Blame the media' thinking was popular even in the 1700s.
A University of Missouri analysis of recent political blogs - i.e., basically meaningless, but fun to talk about - indicates politics are getting nastier due to digital media. Why? The digital world has made it easier for polarized interest groups (which is basically every interest group) to reach other people who are similarly polarized.