Mormon continues his very unsympathetic portrait of Noah and his priests. If Noah were actually adopting a foreign mode of life (with the appertaining religion) then these actions were possibly seen in a much different light by the people who had also adopted that cultural model. For instance, we have noted that while Mormon sees Noah setting his heart upon riches, we have noted that the people may have been doing the same, and approving of the riches that were manifest for their benefit. The consorting with wives, concubines, and harlots depends totally upon our cultural definitions of the types of women described by those words. With the exception of harlots, the wives and concubines could easily be seen as legal wives under a different system (much as we have suggested Jacob preached against).
The "harlots" may indicate that there were sexual unions which were not under the bounds of legal marriage. In many religions, however, their were priestesses who might perform such acts as part of their religious service to their gods. The Vestal Virgins of the Greek world might be an Old World example of what could be described here.
None of this means that Mormon is incorrect in his moral disapproval of Noah's actions. Noah was clearly an apostate from the true religion, and regardless of the social acceptance of his actions, Mormon understood that they were not actions under the approval of the God that Noah should have known and served. It is in the context of Noah's apostasy that we need to see Mormon's comments. Noah had left the values of the true God for the values and riches of the false gods. No matter how well accepted were those practices, they were still the practices of false gods, and Mormon knew and prayed for better.