One good start would be to separate "liberal" from "left". There are some fundamental differences, beginning with the traditional liberal preference for freemarket exchange and capitalistic economic setups.
Has the Left gone too far and become the mirror image of the extreme Right?
No. Obviously not - the extreme Right has control of two of the branches of the Federal government, the extreme Left can't even get a talking head on TV.
Also, considering where I'm posting this thread, what is your definition of the word?
It's been defined by a century of intellectual product and effort.
One can read here:
https://www.amazon.com/Liberal-Imagination-Review-Books-Classics/dp/1590172833
or here:
http://books.wwnorton.com/books/The-Conscience-of-a-Liberal/
Here's a video (sound and snapshots) from Noam Chomsky, famous liberal, on the Tea Party folks when they were new:
Summary: it's "our" (the liberal intellectual caste) fault, for not persuading.
or here, for what "liberal" opinions read like in high style:
https://www.amazon.com/United-States-1952-1992-Gore-Vidal/dp/0679414894
About that last: Like most public and "official" liberals, Vidal has been generally right about stuff and made a couple of successful predictions, including one quite startling call at the very beginning of W's tenure: that W would leave office as the least popular president in American history. Not the worst, necessarily, or the least competent (that would not have been startling), but the least popular. (At the time W was iirc one of if not the the most popular Presidents ever. Asked how he knew that W would do what he did, Vidal denied specific prescience - he said he had no more specific an idea of what they would do than a zookeeper has of what monkeys will do if they get into some place they shouldn't be, but he knew monkeys when he saw them, and he knew what any zookeeper knows: monkeys are trouble. )
But keep in mind that Gore Vidal called himself "conservative", apparently (my read) on the grounds that slightly leftwing libertarianism and liberal thought in general is the traditional US approach and ideology, and has been for hundreds of years now, and his family legacy of this (since before 1700) in America is what he was carrying on. He regarded himself as protecting an established America, of a kind
https://en.wikipedia.org/wiki/Gore_Vidal
So self-identification as a "liberal" does not define the tribe.
"The hatred Americans have for their own government is pathological, if understandable. At one level it is simply thwarted greed: since our religion is making a buck, giving a part of that buck to any government is an act against nature.
- -
'Liberal' comes from the Latin
liberalis, which means pertaining to a free man. In politics, to be liberal is to want to extend democracy through change and reform. One can see why the word had to be erased from our political lexicon."
Vidal on prevalence of censorship:
On Obama's status as an educated man: