Why think it's more 'normal' for a man to have multiple wives and not a woman multiple husbands as you seem to be suggesting?
I don't see how you can read his words as anti polyandry. You lost a great chance to go forward with him in the conversation (aside from the fact that he's busy) because you are trying to turn this into a conversation with a conservative Mormon. But you are nowhere over the target. Meanwhile, genetically speaking, the greater part of polygamy seems to be polygyny; in other words, his point was valid, it's generally contraindicated for our natures. (the word generally is the key, here)
Jesus didn't preach against polyandry, either. He did preach against adultery very strongly, though.
It stands to reason that if I have no issues with gay people being married then I obviously find it acceptable for a woman to have a wife.
Yet they couldn't be open with you if they had a wife and a husband if they are bisexual. It's like the idea that it's okay to be gay but not BE gay.
I don't think polygamy should be acceptable as in legalized marriage as I think multiple simultaneous partners goes against our inclinations and would be destructive to any supposedly loving marriage, especially with children.
I see it the opposite way around. I think polygamy would be a steam valve in a stressful marriage where two people can't stand to be joined at the hip but love each other very much. They could still have a family and no divorce, while being able to evolve their social environment to suit all the aspects of their lives. Without polygamy those couples would either have to tough it out or divorce to have an acceptable, approved living arrangement in serial polygamy (so-called monogamy).
My other main objection would be that it seems very much a one way street where it's men who have all the wives and it subjugates women to essentially a lower order of citizen in a patriarchy.
Even if polygyny was the only acceptable form of polygamy, which it isn't, that would a faulty assumption. An estrogen dominated household where women hold purses and run the house together is not a place for a man to become controlling or abusive. The women could easily gang up and turn the tables; plus it's the man, usually, who has to do extra work while women instead have a fraction of responsibility towards him.
By all means correct me on that if it's actually acceptable for women to have multiple partners also?
God never penned a prohibition against it. Jesus had a chance to speak against it with the polyandrous woman at the well, but only indicated that one was not her legitimate man.
It may be the only compassionate route around infertility for some couples, without destroying a marriage to produce them or denying a birth-father access to his children.
The fact is that polygamy, at least in modern society in the main, doesn't fly.
Think about this: why would it be good for a man to say, by reason of marriage, that the wife cannot have babies because he doesn't want or can't have them? Why force her to choose between husband and the babies? How does that promote marriage, children or women?