common courtesy
Synonyms
Examples
People say 'Why would you learn Dutch? Nobody speaks it. Why not French?' Even the Dutch say that to me! I say because I want to live here, I think it's only common courtesy that I speak the language.
To talk of prayer after admitting he professed no faith was, in my opinion, a breach of common courtesy. In this sense, he did make a social blunder, for which I think he well deserved some minor castigation.
Common courtesy dictates that we never drain the lifeblood of anyone to whom we've been formally introduced.