This, I think, is pretty clear. If you had no intent, you are not threatened. When you're watching Elfen Lied (even although it falls short of the situations envisaged in the above two extracts, but lets just say for the sake of argument), and child abuse is implied (again I stress that this is insufficient, but just for the sake of argument), you have no reason to suspect that it would. What you see on the cover of the DVDs is an adult, humanoid female, and there's no writing in large print saying 'CHILD ABUSE'. A criminal act (for the most part) requires two things to coexist: actus reus and mens rea. The act (possession in this case) and the blameworthy state of mind (the intention to come into possession/maintain possession), if
Watching amv's is a different thing. They are largely doujin and only the fans know what they put into it. On the other hand, given the popularity of Bleach, Dragonball, Naruto, you name it, everyone is preoccupied with making shounen amvs using footage gathered from at least half an episode. What I'm saying is that hentai amvs are rare, bloody damn rare. BUT, your defence applies here as well. An AMV is by definition a mixture of scenes and very often scenes taken from various shows. If you go and watch an AMV made from a loli show, no, you will have no defence, because, obviously, what the hell were you expecting from a loli show? Bakunyuu rofl? But if it is a mix of anime, and there just happens to be a loli scene or frame you never would have or could have expected, you will have a defence.