At a Minnesota fund-raiser, Bill Clinton put his finger on the reason it's so hard to discuss politics or achieve consensus in the U.S.—too much dogma and too little philosophy:
"If you have a philosophy, it means you’re generally inclined one way or the other but you’re open to evidence. If you have an ideology, it means everything is determined by dogma and you’re impervious to evidence. Evidence is irrelevant."
This is a very interesting distinction, and one which pretty well sums up the great political divide in America.
People who subscribe to similar philosophies may argue the finer points of their world view, although they tend to agree on the basic premises. This requires real intellectual work and enough integrity to admit to doubts and uncertainties.
Ideologues, on the other hand, gloss over differences and march together in lockstep, espousing a particular point of view regardless of all evidence to the contrary. They put forth their own version of truth—be it "truth" about climate change, creationism, or the Constitution—and evidence be damned.
Sadly, the ideologues have a real advantage in politics. They can always speak with complete conviction, regardless of the truth or falsehood of their arguments. Thus, John Boehner can falsely claim that the Bush tax cuts created jobs and stimulated the economy; in fact, they added $38 billion to the deficit (one of a series of missteps by the Bush administration that turned a $128 billion surplus into a $490 billion deficit).
It's hard to talk to ideologues. They tend to be firm in their (sometimes literal) conviction that God is on their side and evidence that supports another view is the work of the devil.
How can any rational person argue with that?