Playing Devil's Advocate here - it's the effect on people that is important. Does the ad entice men to believe that women are sex objects, or does the ad pay out the stereotype itself to incite humour? I'd say it depends on what men's attitudes are towards women prior to the ad. Do men sincerely or subconsciously see women as sex objects and actually believe the stereotype? If that's the case, then the ad will have the effect of further cementing and perpetuating the stereotype, and that's the negative effect people are worried about. What if men already know that the notion of women's supposed role as sex objects is simply a stereotype and is not true? Then they will see the humour in it, laugh, but they will be aware that the stereotype is not true - they will be laughing at the stereotype, not at the women.
Your thoughts?