I'd only be ok with polygamy if both sexes had complete equality with it. A woman should be able to have many husbands if they all agree to it.
The idea that there is only one love possible at any given time in a person's life is a fiction. It's proven wrong every time a man becomes terrified of losing his wife, because he slept with someone else. Why should he care? He can only love one, right? Nonsense!
Marriage is about maintaining the nuclear family. I wonder sometimes if the creation of ownership over the sexuality of another is designed to stave off another sexual/reproductive arrangement that appears more appealing to the individual, yet far less useful to those humans that would harness the labor of their fellow human beings.
The Mosuo tribe in China is a matriarchy without marriage. Women are the backbone of the households. When a woman is of age, she gets her own room and can have anyone she wants over for sex, but they have to leave in the morning. The babies are raised by the households the women were born into. Therefore the women do not fear the lack of economic necessities when it comes to having sex and raising babies. The men do not fear the economic burden either. It's a household issue for the men and the women. This changes the game.
Think of all of the economic work people do just to win or maintain the love of that special person. It makes women seem overly focused on money, when they really just want economic security for themselves and their offspring. It makes men into more controlling people, trying to make other men do not steal their investment of time, money and resources. This is why the sexes care so damn much about cheating, they fear great economic and personal loss. They are not supported by a larger communal household. They are alone or in nuclear family units competing against others for the fiction of money, an imaginary commodity that controls the time and effort of human beings, often created by private hands.
In their culture, they actually get offended and shame people when they try to claim ownership over the sexuality of another. In our culture we get offended and shame people that do not submit to sexual ownership, monogamy or marriage. We call them irresponsible sluts and when they have kids we call them bastards. Perhaps we are jealous. How many people married for 5+ years don't spend time thinking about having sex with other people? They do what our desires compel us to do, but we feel that we can't, because we don't want the social order to treat us like inferiors. So, we join in on attacking them for being the horny human beings that we all are.
If people just had sex whenever they wanted, then how would they take care of the babies? Our economic system pushes us toward marriage. Theirs doesn't. This is just one of many cultures that allowed for a more free expression of sexuality without the sort of monogamy for life marriage that we insist upon.