Arnold Kling writes :
My hypothesis is that progressives, conservatives, and libertarians view politics along three different axes. For progressives, the main axis has oppressors at one end and the oppressed at the other. For conservatives, the main axis has civilization at one end and barbarism at the other. For libertarians, the main axis has coercion at one end and free choice at the other. So here is what I recommend doing when arguing with each:
When arguing with a progressive, start by saying, “It is sometimes appropriate to view particular classes of people as oppressors and other classes as oppressed.” Slavery is an example. Proceed then to suggest that, on the other hand, there are instances in which this way of looking at things is not so compelling. For example, if you think about it, borrowers who obtained homes with no money down are not necessarily oppressed, and the banks that lent them the money are not necessarily oppressors.
He proceeds to do the same thing for conservatives and libertarians. Very civilized and I think, a productive and appropriate way to converse graciously with someone you disagree with.