"dangerous" in that a convention full of people under 16 (sex), 18 (cigarettes, nudity), and 21 (booze) leads to a lot more inappropriate situations (that is, the same sorts of things that happen at any con are more often inappropriate or illegal at a con with a younger crowd).

Also, you keep making false distinctions. I never said most anime was aimed at adults. Do you grasp that media can be produced without targeting a specific audience?