The audacity of the recent actions by immigration officials — separating children from their parents en masse, and warehousing the kids indefinitely in underequipped facilities — explains some of the recent abandonment of political civility. President Trump’s very nature, regardless of actions, explains some more.

But only some. Civility has been under open assault for a while in the U.S., and the root problem goes a lot deeper than the words or policies of any one president or party