You'll notice that Dr. Manhattan's exposure was the last in my list, and that was with reason... it was never presented "that way", although some parents would probably find it distasteful whether their kids saw it or not. That's mostly because of our societal mores.
In the meantime, you reminded me of a few more scenes that only the most irresponsible person could assume would be acceptable viewing for an 11 year old:
Cold-blooded murder of a pregnant woman
The entire child killer scene
Young Rorschach biting another boy's cheek off
Not to mention, how is a child supposed to understand the whole theme of Rorschach's mother being a prostitute?
How about Sally having gone back and willingly sleeping with the Comedian AFTER he tried to rape her (and knocked her around)? If a kid is old enough to understand the attempted-rape scene, but not really old enough to grasp just how fucked-up people can be, then that whole theme will confuse the hell out of him (or, worse, her) and maybe plant a terrible seed that will bloom into some warped perceptions.
Let's be honest with ourselves here... kids today, despite being coddled and sheltered from the outside world, are getting more and more fucked up. IMHO, that's because parents aren't paying enough, or the right kind of, attention to their kids. They assume, incorrectly, that there's nothing in their homes that can damage them, and that all the danger is outside, lurking the streets with a trench coat and a bag of lollipops. Meanwhile, they let their young children watch grown-up movies, TV shows, play M-rated video games, and surf the web unsupervised. Nobody wants to lord over their children the way we perceived that our parents smothered us... but, sorry, giving them free reign is a recipe for disaster. The new-age parenting techniques of constant praise and minimal discipline are failing. We've got 12 year old girls dressing like whores. If you let your pre-teen wear a pair of sweatpants with ANYTHING written across the seat, or a t-shirt that says "sexpot" or similar, you are a failure as a parent.
Of course, this is my opinion, and I'm sure I'll get modded down and probably a hundred responses of "my partner and I let our 6 year old use the computer unsupervised and she has never looked at porn and is a polite and independent little treasure!" Great, good luck with that in another 6 years.