The debate on civility seems to miss that this isn't a binary.
The opposite of a good act isn't automatically a bad one. So, while being civil because one wants to live in a civil world is a good act, that doesn't mean not being civil is wrong.
Civility can de-escalate and build empathy, but it doesn't automatically stop five people in masks with bats; so instead of making it either civil or not, consider the nuances of self and situation then pick a reasonable response.