I don’t think acknowledging morals as relative to the culture they exist within exempts decrees of immorality. Relative to their culture, it is. Should they speak from the point of view of a culture that they don’t understand? I personally think it’s a sliding scale where, to the extent it harms other people, it needs to be viewed more objectively just, and where it doesn’t harm, it’s fine being a difference in opinion. The only downside to this is that sometimes you don’t know enough about a topic to know there are victims, and so your prescriptive thoughts can change very quickly about the morality of it. Perspective is important and should always be maximized to avoid this problem.