Imagine if they showed Lisa's vagina instead of Bart's penis

This movie would be X rated. It would be condemned by women's groups for pedophilia and sexualizing little girls and rape culture, etc... Instead, the promise of seeing a young boy's penis was made into a highlight of the marketing campaign. Why is that allowed? We see this double standard all the time with American movies. The Hostel movies and others like it freely depict in graphic detail male genital mutilation, and create the most contrived situations just as an excuse to show it. Female characters will often chop off the genitals of male characters for the purpose of revenge or comedy. Female nudity was always limited to a brief flash of public hair in romantic context at the most, but now even that is a thing of the past.