HaLeivi > Just because a sensibility for a certain behavior, or Middah, didn’t exist in the past, that does not make it wrong.
totally agree. All behaviors towards people are conditioned on their sensitivities and expectations. A yeshivish example I heard is a comparison on how to react to a bochur erroneously suddenly saying “no tachanun today”. In old Poland: Gabbai clears the space near the bimah and embarrassingly invites “the new Rosh Yeshiva” to take the place. In more modern times, R Ouerbach whispers the gabbai “skip tachanun”.
I don’t see why the same approach is not applicable to relationships to non-Jews. Truly, we need to be realistic that we can rely on good relationships. They can always sour quickly and often did in history. Same as peace in Europe suddenly ended in 1914 after several decades and lead to a half- century of destruction. But this should not prevent us from being fair and grateful and good citizens.