@Extrain,
Ken, would not the following conclusion just fall out of how Cultural Moral Relativists view the situation? At what point does the beliefs of conquered culture B cease to be true within B's culture when A conquers B and the cultures become one?
Thesis: Every culture determines what is morally right relative to that culture, so,
Culture A believes A is true.
Therefore, A is true and morally right relative to culture A.
Culture B believes ~A is true.
Therefore, ~A is true and morally right relative to culture B
A conquers B. Culture B becomes part of culture A.
Therefore, the might/force/command of A makes A true for sub-culture B.
So, the might of A determines what is right for sub-culture B.