It's really the ad hominem, hate-laced attacks from the radical right--typlified by Fox News and AM talk radio-- which are responsible for the current divide, not liberal policies.
It's really a fight between truth and lies, mostly, not right and wrong. Newt Gingrich and Donald Trump are personifications of a concerted Republicans strategy to warp and twist the political debate now and in the recent past, but they are merely two of the more visible ones, shamelessly peddlng falsehoods in the name of the super-rich elite, and their corporate, profit-above-all-else machines.
Liberal policies are for the most part grounded in reality, sprinkled with a bit of idealistic fantasy. Conservative policies are mostly an unfortunately effective way to disrupt and retard progressive change.
Bill Maher is a hero of mine, but he's not right 100% of the time