For example. In traditionalist Arab cultures polygamy is legal. In most western cultures it is not. Who is right?

The culture that allows polygamy is right because they also allow monogamy. They don't try to make their preference the only one that's legal. There is nothing inherently wrong with polygamy.

If all the participants are there willingly, there is absolutely no justification for making it a crime.

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.