The link which you sent me is a website which has been designed by very ill intended individuals as is shown by their extremely poor referencing, blatant lying and shallow understanding of the narrations and historical evidences.
In regards to the personality of prophet Muhammad (s): every individual who surrounded him, whether his wives, friends or even enemies attested to his excellent behavior and highest level of justice, dignity and respect. He was at the highest pinnacle of human perfection as described by Allah (swt) in the Quran [68:4], and it is thus impossible to even consider true what this website accuses him of.
As a family man, he was the best of husbands, who treated his wives with utmost respect and love, and ensured that he granted them all their rights, at times even sacrificing his own rights, as highlighted in the Quran and in traditions.
It would be an insult to attribute the claims on this website to any normal human being, so how could we even consider them true for the best of human beings?
The discussion is a lengthy one and there are various books written on the reasons behind the prophet marrying many women. One of which is the following: