Interesting way to look at things. Polygamy is what ensured the survival of the homo sapiens species evolutionary speaking. Polygamy ensured for more offsprings and seeing that death was common in those times, having a lot more offsprings was the only way to ensure continuity of species.
But the world has changed greatly since that time. Survival is no longer the reason for the human existence. I think if people come to realize that, then they would agree that polygamy is unnecessary.