We are, but we don't have to wallow in the craziness of the cognitive errors that are the legacy of our stone-aged brains.
If someone disagrees with us, instead of looking for evidence that our view is correct, why not look for evidence contrary to what we believe? It might be a bit uncomfortable, but it could lead to more accurate information.
When someone sends us email that is too good to be true in terms of proving a long-held belief, why not check it out on Snopes.com or FactCheck.org before forwarding it to someone else? It could kill a delicious bit of gossip, but YouTube videos of some kid trying to skate board on a two-story railing can be entertaining too.
If someone pontificates on an issue we know little about (except what our political leanings would suggest is the correct position), why not ask questions instead of taking sides? A couple of good questions to ask: what do people on the other side of the issue say? Why do they say that?
If we have a favorite right- or left-wing columnist, why not try reading someone on the other side of the political fence once in a while? NPR often teams David Brooks and E.J. Dionne, and they almost always manage to be informative and entertaining without resorting to name-calling, insults, or sarcasm.
Finally, why not adopt as a motto the sign posted in many of those Republican caucus rooms last night? "Good manners are practiced here."