What are things that divide our views as people? Before you say Coke and Pepsi, I think here's what I feel...
There's one word. It's faith. Now, faith itself can be in many things apart from religion. In other words, an acrimonious debate between an Indian and a Paki can have same intensity as a fight between a Red Sox fan and a Yankee one or an argument of Mac over PC..
In either case, the two parties involved in the debate have associated themselves and aligned to a particular "faith". The Red Sox guy for instance is so "faithful" and loyal to his team he refuses to budge. So the follow up question should be, how do we become so tightly coupled with our respective faiths so as not see the opposing view clearly? To paraphrase; what is that drive that keeps us from being in other party's shoes?
Come to think of it, faith, whether in a religion or an idea, or a political party, or an ideology, or a set of convictions, or a set of principles, or a person or prime minister or a president... Why is it so strong that we bargain loosing sleep, sense of equilibrium and even friends at times?
I think the answer lies in another word. And the word is - EGO. It's almost like a game. We see losing an argument as a Loss of a point, say, in a tennis game. And try to make a comeback. Our ego, takes over and we try to reassure ourselves that our "faith" in an xyz thing is well placed. Even sacrosanct. And it should not be shaken, because it is pure.
A person however broad minded or "smooth" s/he may sound, has a set of tightly coupled faith umbrella. Let me give the example of my wife. She's as apolitical a person I have seen. She is neither liberal nor conservative. She did not support Obama in last elections but neither was for McCain. That does not mean, she does not have a mind of her own :)
She simply is detached to these things. But does that mean, she does not have faith and ego? Nopes totally wrong. You have to ask me to what it is like arguing with her. She won't budge a cent.
That's an indicator that she has tightly coupled faith. Not in Religion or Political Party or Chicago Bears. But she has her own set of convictions that if questioned can rile her up real good.
My point is, debates over Politics,Religion,Sports are probably more visible form of faith based divisions. But there are many many issues we all consciously or sub-consciously have aligned ourselves with. And these are nothing but our own respective faith in those entities. And once a person associates herself with a certain set of ideas, it's hard to decouple her from it. We are all reasonable and un-reasonable in few areas. No person is completely and absolutely reasonable in ALL domains; although our fanaticism may vary!