I only support monogamous marriage. I draw the line at gay marriage. Plural marriage would require our laws to be completely overhauled to deal with children, inheritance, estates, divorce, etc. It would be a nightmare. That's not even getting into the social consequences. Polygamous societies are more violent and less stable according to studies. Women and children fare less better.
I agree; polygamous marriages generally lead to one party monopolising the majority of power and influence - especially when socially imposed gender roles i.e. husband as bread-winner & provider come into play.
Monogamous marriage was a boon for the rights of women since it promotes more equality between the spouses.
I disagree; monogamous marriage does not inherently promote more equality between spouses as compared to polygamy. For the vast majority of history women have had inferior rights compared to their husbands in societies with monogamy as a social norm. Going back as far as the ancient Greeks, Athenian women were seldom allowed to leave their homes, be seen in public or communicate with men other than their husband or household slaves.
Were it otherwise the rights of married women in monogamous societies would have been inherently & consistently better than those in societies where polygamy was a thing but they were not. Women have been treated as chattels and the property of their husband until as recently as just over a century ago in 'the West'. Look at how Victorian women were treated; their identity was effectively erased when they married.
Believe it or not, marital rape wasn't outlawed entirely on Great Britain until 1991 (in England & Wales; Scotland outlawed it in 1989).
I also think polygamy is morally inferior to monogamy because instead of one person as a life partner to grow old with, you have any number of people who you have to ration out your romantic and sexual love for. Romantic relationships take time and effort. One person is daunting enough, but multiple??? There's usually a primary partner and secondary ones. There's a system of favoritism. Someone is going to have to be satisfied with less and I don't think that's fair.
I also agree with this. While I'm not confident enough to say it's in the nature of humanity generally to be monogamous, I think it's simpler, involves less hassle and makes more sense socially to commit to a single partner.