What are the roots of the current divisiveness of American politics/discourse?

[hopper]

It all goes back to Newt Gingrich's decision in the 1980s to wage "guerilla warfare" against the Democrats in Congress.  That led to constant gridlock and disdain for government.

The Democrats had the House Majority in the 1980's though. Yes the Republicans had the Presidency for nearly all of the decade except for 1980 when Carter was still in the White House. Also, The Republicans had the Senate Majority for a little over half of the 1980's(1981-1986) while the Democrats controlled the Senate Majority for the other 4 years of the decade(1980, 1987-1989.)

[hopper]

this all why the far left called bush

-illegitimate
-war criminal
- a dictator
- somebody who is a threat to American democracy
- called him racist


All of these were so outrageous that DU , TYT , all the far left commentators should apologize for using such malicious lies against Dubya

so anybody from the far left willing to apologize for this

For what?  Those are pretty standard lines used against any President.

Calling someone a war criminal you think is not outrageously bad .

W may not classified a war-criminal, but his foreign policy decisions, especially the invasion of Iraq, was a complete disaster. He and his neocon administration lied the heck out of it and made stuff up to legitimate a war. Not to mention torture and all the stuff that ruined our standing in vast parts of the world. For sure, Saddam was a horrible dictator, but terrorism and ISIS are even worse. It's mostly the fault of Bush Administration, although I acknowledge that the end result was not W's intent. But they are the result of wrong decisions made by this administration. The other points on W are garbage, he's neither a racist nor was he a dictator, though his 2000 victory is at least questionable.

But if we're talking about hate for a president, we should also talk about the far-right and Tea Partiers and their bigotry and hatred for Obama. They floated the stupid idea that he was born in Kenya, that he's a muslim etc. They did everything to damage this president, mostly due to racism. They hate him more than they love America. For sure, Obama is not perfect and he made some mistakes. But what the Tea Party did with Obama is a disgrace- and shameful.

Most Tea Partiers weren't racist. Some were. There are crazies in every crowd.

[hopper]

50% - The Republican Party
50% - Baby Boomers

Baby Boomers-I don't know what you mean that Baby Boomers are 50% to blame for political polarization. A lot of Baby Boomers voted for Obama both times(2008 and 2012) I think.