Peter Wehner makes it:
Civility is not a synonym for lack of principles or lack of passion. They are entirely separate categories. Civility has to do with basic good manners and courtesy, the respect we owe others as fellow citizens and fellow human beings. It is both an animating spirit and a mode of discourse. It establishes limits so we don’t treat opponents as enemies. And it helps inoculate us against one of the unrelenting temptations in politics (and in life more broadly), which is to demonize and dehumanize those who hold views different from our own.
He goes on to cite Abraham Lincoln as a model.