Civility is a two-way street, an obligation between two people. It’s like the playground rule of keeping your hands to yourself, which still lets you defend yourself against an attack. Kids have to keep their hands to themselves, so long as others do the same.
So people tend to be overly sensitive to apparent incivility from opponents, and often feel free to respond with incivility themselves.
The result is tragic. People across the political spectrum agree that incivility is poisonous. However, rebuilding civility requires people to trust their political opponents and believe they are well-intentioned and willing to reciprocate.
Partisan divides have rendered many Americans nearly incapable of regarding their rivals in so positive a light. Civility might be practically impossible today. At the very least, it is more difficult than many people suppose, because of the human tendency to feel contempt, not compassion, for opponents.