From one woman to another, I suggest you ignore those debates with those dudes. They probably aren't even married and are sitting there dreaming about their 4 wives. I've seen those types before. They'll be lucky to find one woman to put up with them.
I've studied Islamic Law for years now and I've only gotten the impression that polygamy is permissible and it was actually a limitation on 7th century Arabia, where they had more than 4 wives. There is a requirement that the wives be treated fairly and equitably, which is difficult to do. There's also the problem of this being illegal in the US. But I guess it's still legal in other countries.
I've traveled to many predominately Muslim countries and I'm seeing that it's becoming highly unacceptable. I've only met 2 men in my entire life that were married to two women. The first did it because he wanted a divorce, but his wife asked him not to so that he would take care of her. She didn't work and didn't want to. My mom knew her and said she was exceptionally mean, rude, and verbally abusive to her family members. She didn't care if he married someone else. As for the second guy, he did it for more selfish reasons (i.e. he wasn't attracted to his first wife anymore), and from what I saw, his community grilled him for it and everyone looks down on him for what he did. He seems to highly regret his decision now and is constantly stressed. His parents were exceptionally angry at him and stood by his first wife. In both instances, the first and second wives were intelligent and educated. They all were in countries that would afford them protection and support if they decided to leave.
Lastly, if you don't like it, make sure to be clear about that and everything important to you if you ever consider a marriage. Go for the guy that admires you and you only. All the guys I considered for marriage (my husband included) disliked polygamy, but I guess it's possible you could come across someone that approves of it. Clearly, from the debate you went through, those guys are out there. If they can find someone to put up with it, power to them. They're just not for ladies like us.