All Muhammadans are commanded by Koran to copy the life of Muhammad, the perfect life lived by the perfect man.
That's why they can marry nine year old girls.
Yes. Christians are taught that Jesus lived without sin, but are not told to live like him in every way. Male Muslims are told Mohammed is the example for all of them to follow. ("perfect" might be the wrong word because Mohammed did err a few times, for intance about the three goddesses and when he slept with one of his wives out of turn)
If Muslims are going to use Mohammed as the example of a perfect or near-perfect role model, I think it's perfectly fair to criticize his behavior.