What is your evidence for this? If a man has the means to support more than one wife and treat them justly, he can take a second, third and fourth wife, even if it is just to satisfy his sexual desire. After all, isn't that one of the main reasons why Allah and His Messenger encouraged marriage in the first place - so that it provides man a lawful means for fulfilling his natural urges? Islam makes man responsible for his pleasures. So if he wants to take multiples wives, he must also be prepared to face the responsibilities that come with it. Again, I would like to see your basis for this conclusion. As long as the man is just and has the means, nothing in the Shari'ah has prohibited him from taking more than one wife.