I'm not sure if this has been brought up (some posts have been removed and I haven't carefully read through every page here) but what of this?
Muhammad's sunnah (practice) was polygamy, the Qur'an instructs about polygamy, and there are Muslim leaders in the West who want polygamy. Islam is then a polygamist religion.
In Islam a man is allowed multiple wives and an unlimited number of slave girls.And those (men) who preserve their chastity Save with their wives and those whom their right hands possess, for thus they are not blameworthy. (Qur'an 70:29-30, Pickthall)However, while Muhammad had many wives and slaves girls, and taught this in the Qur'an, he would only allow his son-in-law, Ali, to have one wife. Why? Because Ali was married to Muhammad's daughter, Fatima.Narrated Al-Miswar bin Makhrama: I heard Allah's Apostle who was on the pulpit, saying, "Banu Hisham bin Al-Mughira have requested me to allow them to marry their daughter to Ali bin Abu Talib, but I don't give permission, and will not give permission unless 'Ali bin Abi Talib divorces my daughter in order to marry their daughter, because Fatima is a part of my body, and I hate what she hates to see, and what hurts her, hurts me." (Bukhari: volume 7, book 62, number 157, Khan)What hypocrisy!
Polygamy is fundamentally different to monogamy. In a monogamous marriage the man and women both promise to be sexually faithful to each other and to bind themselves to each other alone. However, in a polygamous marriage only the woman is bound to the man and must be sexually faithful to him. The man is free to keep looking for other women. Polygamy completely changes the way a man thinks about women and what it means to be faithful to them.
Response: First and foremost, islam does not allow unlimited slave girls. As far as the hadith is concerned, in islam, one should marry a co-wife if the woman is in "need." Meaning, that the woman has no other means to support herself, not that a man can freely roam the earth and marry whom he pleases. Coming to the hadith, it says that the prophet hates what his daughter would hate, meaning that she would not like the idea of a co-wife. So the prophet's disapproval of the marriage is not unfair because the main principle of polygamy is for it to be agreed upon and should be to the liking of the wife as well. If the wife does not like it, one should not do it. This is the case for any muslimah, whether related to the prophet or not. The wife herself should consent to it as well. In the case of the hadith mentioned, since Fatimah did not consent, then and and then, does the prophet say that he will not marry them.