I see this brought up, like clockwork, every time Foucault is mentioned. Since this is a philosophy comm, and Foucault was one, I want to bring up something very obvious. That was not a libertarian position, and it should be obvious too that 1970s France and its political culture was absolutely nothing like the contemporary US political culture. Most of the signatories, like Sartre and Althusser, were some sort of communist. At the very least, this should make one think: Well, why so many French intellectuals signed it? For those actually curious about the legal, social, and historical context behind that petition:

http://self.gutenberg.org/articles/eng/French_petition_against_age_of_consent_laws
http://self.gutenberg.org/articles/eng/Sexual_Morality_and_the_Law

If you are familiar with Foucault, the above is an interesting historical document about how Foucault's political theory found its expressions in practice. It might help you cancel him better because of that reason--if that's the goal--because it provides an avenue to cancel his entire intellectual apparatus. One fewer author to read, phew!