Incest is pretty universally considered wrong because of the grave damage it does to the offspring. Children of incest have a MUCH higher rate of birth defects of all sorts. Polygamy is wrong, in my opinion, primarily because of the way in which it is practiced in the US.
In the US, 90% or so of those who practice polygamy do so by marrying children to old men, and that is wrong because children (or coerced women) cannot give free and informed consent. Beyond the concerns about consent, the only practical problem with polygamy that I see is the need to create a mechanism for divorce, child custody, inheritance and so forth.
I cant really gove you an answer,but what I can give you is a way to a solution, that is you have to find the anglde that you relate to or peaks your interest. A good paper is one that people get drawn into because it reaches them ln some way.As for me WW11 to me, I think of the holocaust and the effect it had on the survivors, their families and those who stood by and did nothing until it was too late.