Is there a gene that pushes us to extreme points of view? In the 1900's psychology went through periods where genetics were considered the main determinant of behavior. Then behaviorism reared its head and people argued for the nurture side of nature v. nurture. Now, thankfully there is a paradigm that states the two sides are mutually important depending on context.
What does this has to do with anything? Consider behavior and rigidly held views. Look at the idea that there are two political parties and that the government is often gridlocked by partisan wrangling that squelches ideas that could be beneficial to both sides. Most recently, this was demonstrated by the those Clinton supporters who were so invested and locked into their point of view that they would rather vote for McCain than for Obama. Not making a political statement, just using it as an illustration.
Dichotomies seem to be a human foible. "You're for us, or you're against us." "feminine v. masculine", "left v. right".
The truth though is often somewhere in the middle and the solutions are an acknowledgment of both. Maybe we seek black and white answers because they are the easiest to deal with. Set rules, right or wrong, mean there is a compass and in certainty people find security.
As a person who is often extreme and unreasonable, as someone who too often inserts himself into public arguments without listening and understanding the other side, these ideas feel right to me, but practice of them is not often easy. We're hardwired. But that doesn't mean the hardwiring is restrictive. I think it can be overcome---with practice.
Maybe not by me, but then I'm a hypocrite.