I have a point to make, and need to clarify that I am not denouncing polygamy.It would be haram to do that. We can express our personal preference, but not reject it as a concept. However, I will clarify a difference in 2 examples:
A)A man tells his wife, you are a wonderful wife, I love you very much, I cannot say anything wrong about you. However I'd like to get married because of such and such..Sometimes, or marrying a widow with orpphans, or a lady that is hardly having any proposals it could be for his own personal reasons. The outcome would be down to them, but the approach is what is vital here.
In this example, polygamy will be explored in its own right. He hadn't referred to her or convinced himself that she's a bad wife and he's on a mission for a better one.If it does happen, then the wife's position and feelings are protected. She is more likely to be mentally prepared.That is part of doing her justice in polygamy.
B) or.. a man decides to marry again, , tries to find faults in the wife as an excuse to get married, runs away from a problem rather than work together to solve it, a problem is his own sometimes, like he is bad tempered, or abusive, marrying another comes up in every argument, in jokes (which is anything but funny).
In this example, the man assumes he is going to find happiness somewhere else. But he's really created problems. By highlighting faults in his wife he's is destroying her confidence, and if he is sincere enough with himself he would realise that he's not free from faults either. He hasn't explored ways making of the marriage better. Ofcourse his wife will resent the topic and his actions. Ofcourse there will be masses of problems in every step for both of them all through. Injustice was made already because it all started wrong.