Although I agree with the skeptism on the Adult Forum I don't think "because it's an anime forum" cuts as a reason. There are plenty of anime and other interest-specific forums that include other types of forums. Proof in itself is our Cyber Lounge, Sensory Pleasures and Debate forums.
It seems like Meiji Imaru wants is to discuss other things aside from anime with anime-pals that aren't easily offended and are going to have well-thought ideas and spend time thinking and posting on subject. And there's nothing wrong with that. Just making an entire forum seems a bit much though... there are other ways to solve the issue, I think.