"Polygamy can work but there is an inherent instability in its structure since it almost impossible for all members of the group to be equal"
the argument made in the original post is that polygamy is unworkable because of inequality in groups of more than two (because two persons cannot be unequal? Have pre-nuptial agreements been eliminated? Have unions between persons of different status been banned?). The person to whom you replied simply stated that the inequality of groups would also preclude democracy from working. How can a system of government and/or a system of social interaction based upon the assumption of equality work if people cannot actually be equal?
I have replied with the utmost amount of discretion. When I am misrepresented, I need to response appropriately. I believe that I did.
I do apologize if anyone is offended by my mostly objective statements. I do not know what those who are offended can do to better comprehend what I have written.