God tells Muslim men in the Quran that you can marry two, three or four women of your choosing. But if that you are unable to deal justly and fairly between your wives then you should only marry one woman. So what would be unfair is if a man married to two or more wives and was favoring one over the other or treating one better than the other.
Beyond that, forced marriage is not allowed in Islam or any civilized society. Polygamy is always practiced by consenting adults who know their rights.