Courtesy as teacher

I've written at more length on the topic of courtesy before here and here and here.

I've heard it said that if you want to hate a man, do him an injury. Conversely, if you want to learn to love a man, do him a kindness.

If courtesy is a kind of attenuated love, then the everyday practice of it should train me to appreciate a bond, however faint, between me and my neighbor. The everyday absence of courtesy will also teach me something. Will it cultivate dislike for my neighbors, or merely callousness?