Interesting thoughts as to relative levels of civility. Let me give you a different lens. I think incivility comes at least in part from not witnessing or having a personal connection to the damage we are doing by being uncivil. Not many of us have the stomach for deliberately inflicting harm on others when we have to witness the impact.
On a big scale, the turning point in the Vietnam war came when images of the consequences of our actions started showing up in our living rooms on our TVs. The reverse has happened, to some extent, in the Middle East via careful message control (and changes in how the war is being carried out). Photos of coffins returning home were banned in the early days because of the lessons the government learned fromf Vietnam. And now we are increasing the unmanned drone missions which distance us even farther from the consequences of the actions we are taking.
Back to conversations - in online conversations, the ones which tend to be less civil are the post and run sites like ohio.com - and the more civil tend to be the ones with members who post regularly and get to know each other (even if getting to know each other is limted to knowing each other other via a screen name). (Although I am quite impressed with the thoughtful responses to the article which is related to this conversation).
In real life - the most uncivil behavior directed at me has been by people who didn't know me, with whom I had a one time encounter in a situation in which I could easily be stereotyped. It is rare that anyone I have an ongoing relationship with behaves uncivilly - even when we hold polar opposite viewpoints.
Now - I'm not sure how dueling fits into that scheme - or how common it really was.
I agree that modeling civility is critical. I've been working on that a fair amount recently - both as a way of responding when incivility is directed at me, and when I see incivility developing between others. So far, what I am doing is being noticed - which actually surprises me. I wouldn't have said I was behaving that differently than I usually do. Some people have responded in kind.But I don't know that isolated individuals modeling civility - no matter how perfectly and how regularly - is enough. So my question is how do we get others to move beyond this sentiment - that civility is only valued until someone throws the first stone (posted in the comment section on Ohio.com):
"I think this whole conversation is really missing the point. In general, it's a good idea to be civil unless someone verbally attacks you then have at it. "
Stones are pretty easy to find - even when they weren't lobbed at us intentionally, and if that is all it takes to justify abandoning civility, it will be pretty hard to stop the cycle.