Education vs. what is right

When does education step on what is right?? Do we as educators have the right to use material that is not school appropriate to teach a lesson?? When does freedom of expression go to far??
This is what is going on the new English teacher decided to teach his English Comp I class about advertisement and talk about what is OK and what is not, basically the sex sales side of advertisement. I think this is a great thing for the dual credit English comp class that is about to be thrown out in the real world and thinking outside the box, not for freshman who are trying to figure out their own bodies and their place in the world.
He had the students bring in the most sexy most racy adds that they could find that was trying to sale a product. He then posted the ads in his class room, OK its his classroom, he then put up an huge college in the hallway (his classroom is located in the Freshman hallway) with alcohol and nearly naked or completely naked people on them.
Here is my problem, I don't like the fact that we expose our children to all of this crap on a daily basis anyway without anyway to protect them, but must they sit in a classroom and look at pictures of what society thinks is the perfect body for 90 min. and then must it be placed outside that classroom where there is no guidance to what is being viewed just what they see??
Is it appropriate to tell our students that they can't dress a certain way and then post material that is not school appropriate for viewing? Is it right to censor poster that the student create but allow information to be posted without guidance?
When does educating our students cross the line??