https://en.wikipedia.org/wiki/Golden_Rule
The Golden Rule is the principle of treating others as one's self would wish to be treated.
In other words, if you wouldn't want something said to you, don't say it to someone else. And yes, I defined it already in a recent post.
Act civilly:
in a civil manner : POLITELY
1a : of, relating to, or having the characteristics of advanced culture
b : marked by refined cultural interests and pursuits especially in arts and belles lettres
2a : showing or characterized by correct social usage
b : marked by an appearance of consideration, tact, deference, or courtesy
c : marked by a lack of roughness or crudities
2 b and c apply here.