There is an interesting article in the Wall Street Journal titled "Darkness Too Visible" (Link to article) by Meghan Cox Gurdon in which she includes the sub heading, "Contemporary fiction for teens is rife with explicit abuse, violence and depravity. Why is this considered a good idea?". She makes the point that there is too much extreme violence and explicit sexual content in YA literature today.
I agree with her to a point. While I am not in favor of censorship and banning books, I think parents have the responsibility to know what their children are reading and to control it if they do not feel it is appropriate. It is also not responsible parenting to have no idea what your kids are reading. That is not permissive or enlightened - it is lazy parenting.
Some argue that Ms. Gurdon and others who agree with her cannot see that writers of such depravity are helping young readers by teaching them about what the world is really like.
I say that it is a bullshit excuse to say that this extreme violence and sex is being written solely with our kids' best interests in mind. These writers are not some sort of quasi-therapists or inspirational figures who are seeking to enlighten our youth - they are simply profiteering and taking advantage of the market.
Still writers should write what they want, and they should do so to try to sell their books. You have to be honest if you want to be a writer.
That's why I think it is the parent's responsibility to make the decisions about what is appropriate.