Because we have eyes and brains and we use language to describe what's going on. There might be some instances of people who called themselves leftists who opposed something which we're now referring to as a leftist agenda. It's not a perfect black and white classification scheme but the deep link between leftism and globalization is painfully obvious to anyone with a brain. We're polarized because we disagree, deeply, trying to mix up the language used to describe that disagreement isn't going to make us less polarized.
If core parts of what "left" and "right" mean are subject to re-definition every 4 years, maybe the polarized tail is wagging the dog.
There is 'global left/right' and 'local/national left/right' now.
The 'global left' is exemplified by UN.
The 'global right' exemplified by WTO.
Often, the 'global' version of a movement can be in conflict with the 'local' version.
This is seen clearly: 'global leftists' care about migrants - a lot - but immigration can be hurtful to the working class of the host nation. Mass importation unskilled labour = wage suppression, it's just an economic reality. 'Global lefits' might use negative terms such as 'lazy Americans' or whatever - which demonstrates the rift - 'working class' Americans are the 'traditional base' of leftists/labour organizations.
This is most acutely seen in the UK, where the Labour vote has been split - most of UKIP (nationalist) votes came from Labour - who are now more of a 'globalist left' party.
The Tories under May are a more 'traditional right wing' party, whereas the Liberals (i.e. Classical Liberal, which in America would be more akin to 'Libertarian') are kind for the 'pro globalist right wing' party - i.e. trade and business is the most important thing.
'Free Trade' sometimes breaks leftist ideals - because on one hand, it can have directly negative consequences for many workers. On the other hand - it means benefits for the working poor in other nations, and quite a lot of benefits for those who can hold onto their jobs in the host nation (lower prices for goods). Of course, the greatest rewards of globalism to the investing class.
Also - it's usually centre-left activists who care about such issues as 'gentrification'. Well - 'globalization' is a kind of 'gentrification' on a massive scale. The loss of local customs, authentic culture etc. is acute in some places like 'Harlem' - but it's also becoming acute across entire nations - some wealthy, some not.
But I disagree with the suggestion that 'there is no more left/right'.
If you take the perspective that there is a globalist/localist divide in both camps, it fairly succinctly explains what is going in in politics all over the Western world.
This is not a novel idea - I'm explaining what others have already professed.
Some added terminology is necessary because Americans use the term 'Liberal' - which in the rest of the world means 'Classical Liberal' - or in American terms 'Libertarian' - and so the mis-matching of terms creates a lot of confusion.
Due to this, you end up with conflicting viewpoints between upper classes in different countries being resolved on the back of the market. What the working class see's is a system that, on the outside, looks fair, but once you delve any deeper than the surface, you realize it's a system of men not rules; the IRS tax code, for example, cannot be understood by one person, it can only be understood and executed upon by an organization. That's the point of many laws, and how arbitrage is executed against individuals.
As one example of this; I once interviewed at a company named Catamaran, who's entire existence was based upon taking complex contract terms for prescription drugs and lining them up with insurance plans. We've got a medical industry, insulated completely from anti-trust law, producing a massive economic distortion from being able to do things that in any other industry would be criminal. In the middle of this industry, there's a multi-billion dollar company that does prescription management largely for drugs that are developed to treat symptoms instead of resolve diseases. Thousands of people doing a largely useless paper shuffling job.
By contrast, I work for a tiny forging company, not even 100 people, and one of the products that company manufactures allowed an international automotive company to undercut the competition by enabling their autos to reduce fuel mileage by a substantial percentage and they are currently cleaning the floor with every other manufacturer out there. Similarly, we have other products for the energy industry that have were similarly innovative.
Ultimately, this system generates wage arbitrage as a waste product and wage arbitrage generates the erosion of culture as a byproduct; the upper classes increasingly chase values so abstract and divided from reality that have absolutely nothing to do with delivering real value to society or getting anything done. I make peanuts compared to what I could make working at a place like Catamaran, but on the same token, working at Catamaran, frankly like working at most silicon valley companies, wouldn't be honest or meaningful work. The company I work at right now has an authentic culture; Catamaran was, like most companies, a faceless mass with no culture (except for political correctness and other Marxist\leftist ideals which isn't a culture unto itself) to speak of.
Ultimately, globalism as it is right now is self-destructive; we waste our time running around in circles to provide a few elites job security. Technology, as the atom bomb taught us, is sometimes terrifying, and it's going to happen whether we are ready for it or not. Our best and brightest need to be leading, and society needs to have the freedom to choose its own culture and values. Without that, much like face-book today, you're a train headed on a predefined set of track for a cliff.
Wasn't Bernie Sanders both the most leftist and most anti-tpp/nafta candidate? Also Keith Ellison, who's potentially the next DNC chair and was endorsed by both Harry Reid and Chuck Schumer? (and by Bernie Sanders, and by David Duke for that matter)
