I know this type of thing can work. I've seen uncensored forums before and they can be fine.
I find it's not the content of these sub-forums that presents a problem but the people. In some places I've seen 'uncensored' to mean "Say anything you want about other members" which leads to people getting butt-hurt and leaving, followed by people defending the posts saying "It's okay here because this area is uncensored, we can say what we want."
I see nothing wrong with having an area for adult content that might not be appropriate for all viewers (like the mentioned video of the car accident or even nude photos) as long as people didn't treat it like an excuse to openly attack other members and or post material that was purposefully meant to offend everyone, for example, children abusing a cat or racial beatings.
Each good idea comes with its own complications.