A couple of professors in the US have taken heat for showing their students porn. One, a feminist, showed an anti-porn documentary that included illustrative clips of hardcore porn. But if you check out the article, you'll see that the complaint against her includes not only the porn but also making students feel unsafe, with the "intensity of the hostility that [she] expressed toward the university and its administration." I'm curious to see the outcome of this one because the idea that agitation against the institution or administration could make students "unsafe" undermines both academic freedom and the right to take labour action (to the extent that either really exists, anyway).

In another case, the professor showed an explicit sex-education video on "advanced sexual techniques," and received complaints from students and bloggers, but her administrators defended her right to show sexually-explicit materials. 

I've been making my way through a Sexualities special issue on "Researching and Teaching the Sexually Explicit," focusing on research methods and IP issues. I think I will revisit some of the articles on teaching now. (There are none about learning, specifically, but some of the articles on teaching do include students' survey responses to questions about things like how they manage their feelings when they see material that shocks them, what they tell people about the courses, etc.)