Even extremely reasonable people tend to use arguments as soldiers. Here a disability rights advocate Harriet McBryde Johnson recounts her discussions with the philosopher Peter Singer (I stumbled across it on Eliezer's facebook page). Both very intelligent and reasonable people, they were unable to come to any common ground to speak of, due to what seems like their inability to look for simple common issues they can agree on without triggering identity-based emotions and then build on them. I found it a really sad story.