The purpose of marriage in Islam is to build a Muslim family which the husband, the wife/wifes, and the kids love each other, feel happy, and InshaAllah, blessed by Allah.
If a man can build a family like this with more than one wife, why not?. There are some men who could build a happy polygamy marriage. I have meet one of them, he's a businessman, a religious Muslim.
But if marry more than one wife will cause the wives hate each other, it's better if this man marry only one wife.
Polygamy is a privilege that given to Muslim men, but unfortunately this is the privilege that commonly misused by men who actually not competent to marry more than one wife, and do polygamy only to follow their lust. Mostly of polygamy marriage are committed by bad Muslim like them.
They marry new wife after attracted to her, then neglect his old wife/wives. And when other people ask "why you did it?", they answer "What's wrong? Islam allow man like me to marry four wives"
No wonder if other people are thinking, Islam is religion that oppress women.
I agree with some brothers who say, Islam has a bad image not because other people make this bad image, but because Muslims themselves created this bad image.