Even in dialogue, your own style rules your selection. Do not give yourself a blank check of this kind: 'I'll merely reproduce what I think a character like so-and-so would say.' You have to reproduce it in the way your literary premises dictate.
Ayn RandPeople think that a liar gains a victory over his victim. What Iโve learned is that a lie is an act of self-abdication, because one surrenders oneโs reality to the person to whom one lies, making that person oneโs master, condemning oneself from then on to faking the sort of reality that personโs view requires to be fakedโฆThe man who lies to the world, is the worldโs slave from then onโฆThere are no white lies, there is only the blackest of destruction, and a white lie is the blackest of all.
Ayn Rand