Fuck that. They're arresting him for violating a subjective opinion of theirs. It is his right to own cartoons that depict anything at all, for they aren't actual child pornography. The whole point is that possessing child porn implies support of an industry that abuses children, but hentai does none of that. That whole court should be ashamed of themselves. They arrested him because they have different "tastes," while there was no actual crime committed.
We must be entitled to our own thoughts, opinions, and predilections if we are to live in a free country. As much as people find child sex disagreeable, as I do, that collector has a right to own "obscene" material.
I hate the movie "The Happening," but I'd be out of my mind to use this to justify an arrest of someone who owns it.