First, the repeal of the Fairness doctrine has nothing to do with it.  Okay. The left lost radio. But they still have ABC, MSNBC, CNN , CBS, The S.F Chronicle, Boston Globe, The NY Times, The L.A> Times, 80% of the newspapers, 85% of the university platforms, 75% of TV broadcast, th vast majority of Hollywood and Broadway.
If the polarization is caused because they lost one medium, they really are fascists who can't stand dissent.  I would be glad to give money to reinstate the Fairness Doctrice if it were expanded to every other media.

People used to be allowed to have differences and they were  respected.  Today, if you have a view, you get economically boycotted and people try to destroy you.  There was a restauarant in W. Hollywood that gave money to the Prop 8 campaign and there were protests out in front.  

I know it is emotional, but in the 60's when there were civil rights protests, no one's business had boycotts merely because they gave money to one side or the other.

Likewise, the left has protests at people's houses.  Union thugs have gone to private homes and picketed.  The left has gone to the Koch Bros house and picketed outisde a private residence.  30 years ago this was unheard of.  (BTW, no protests are ever reported outside of the Soros humble abode.)

When states or cities had a difference in policy, they didn't urge boycotts of the other cities states.  NY never urged a boycott of the entire state of Alabama, like SF does to AZ.

Also, after Bork, the test became not qualification but politics.  You may not like Bork, but he was qualified.  (Without doing the research, I would bet a larger number of GOP voted for Ginsberg and Dems voted for Alito.  Ditto more GOP for Kagen than Dems for Roberts.  I may be wrong. That is just my feeling.)

Politics has become very personal.  The day after the Bush/Gore election, I had to call a friend about a case we were working on.  Now this is before Bush even took office.  He answered the phone, and I asked how he was.  He said he had never been so depressed in his life. I asked why, and he said the election.  

It is not politics, per se.  It has been personalized.

The Fairness Doctrine was ridiculous.  All it did was squash political discourse on the airwaves since the logic was every programmer had to put on 3 hours of liberal talk for every 3 hours of Limbaugh even if the audience didn't want to hear it.  So they all avoided getting into the muck. Limbaugh was the first to benefit from its repeal but people were starving for points of view different from Walter Cronkite's.  Limbaugh's presence didn't create polarization.  His success was proof that it always existed.

We live in a very self-centered time where people can't imagine that the universe existed before us.  So everything that happens now is "The Worst" and "The Most".  Polarization existed in this country before the Revolution.  There was already a divide between parts of the country based on economy, culture, etc..  It was always here and it will always be here.  But according to Priapus and Bill Clinton it's all Rush Limbaugh and AM radio's fault.

And we are laboring under the mis-aprehension of prior "unity."  Why?  Because there was a sense of unity during WWII, after which most of us were born.  It began to slip away by the mid-50s as the inevitable pressures took hold.
But the original colonies had such divergeant goals that it was difficult to put the country together to begin with.  Political differences quickly led to the rise of parties, lamented by the Founders.  Discourse was vicious before 1800, to the point where today it would provoke libel suits.  There was North v. South, East v. West, property owners v. the working man, etc.  Waves of immigration provoked nativist backlash like the "Know Nothings."  Then there was the Civil War and Reconstruction.  More waves of immgrants and the Industrial Revoltion led to the rise of unions and class warfare.  And we're not even to the 20th century yet!  Need I go on?
The great thing about this country is that, despite all the polarization, we continue to innovate and grow.  But don't expect the polarization to end.  It's an old phenomenon.  And it's human nature.

Although robust at times, the Brits have rules about the limits of parmlimentary debate, and iwhile it is fair to mock positions, t is not proper to engage in personal insults.

I forget who it was, but one politician was censured for saying that half of the House of Commons were a bunch of idiots.  Realising he may have crossed the line, he aplogized, saying he withdrew his prior statement and half of the house WERE NOT idiots.

i.e., brain got taken over by babblers on on the news media and came full circle with Blogs and Internet, You Tube, Twitter, etc. Soon we will be back to the stone age.

The Republican party has gone to the extreme right, and the Democratic Party has moved to the right as well. There's some push back on that, but there's nothing much to show for that so far.

That's not polarization, that's just one of our two political parties going batshit crazy, while the country falls apart.

Most people cannot carry on an objective political discussion. There is one political position in the US and it is the capitalist political position. Its like belief in god and religion. If you are christian then your religion in many ways defines your perspective of both other religions and god. Most people in the US are not members of the capitalist class so they have a warped perspective of US politics.