I'm actually rather facinated with this thread as the concept of "should" drives me to two different conclusions.
By the law he "should" be convicted and sentenced as he was, because realistically he could've saved the money and moved to Japan where the laws about such content are much different. But he chose to stay in the USA where his conduct is illegal and his responsibility to know as such.
The other "should" however leads me to believe that this is a morality flaming issue with the idea of possessing illitrusations in this manner is wrong, and while this may be up to opinion and interpritation lemme go ahead and takes both positions on this one.
First, the con, which seems to be the more popular position to take on this subject. With the many well known cases of child abduction publicized in the states it's easy to take a pre-emptive position and say that such material will only stimulate child predator's urges in such a way it symbolizes a pot of water waiting to boil over. It may be wise in a sense to restrict such material now to see if it actually works in practice, since if it doesn't then one can always lift a ban and less damage has been done.
However, allow me to play the devil's advocate and state the pro, human impulses and urges can also be described as a pressurizer, filling with steam until the container's limit is reached and without a release port the whole thing will blow. Well if you look at it that way then one could assume that possessing such material would be an innocent port to alliveate such urges in a much more safe environment, since ACTUALLY performing these acts is not required to get the desired product. This is an arguement that is closely similar, similar not relavent, to the violence in video games issue. Just because people partake in these activities in a much safer environment where actually hurting people isn't nessecary, does not mean that they are planning to enact them in real life, from personal experience ending a day with mercilessly lighting an enemy or two up in Metal Gear Solid or Unreal Tournament was just the thing I needed to relieve the stress that would've otherwise led me to committing such acts in my high school, having an opposite effect then was claimed they would have.
Anyways, I thought I should bring up both points to this arguement since it seemed that many people wanted to outright speak in defense of owning hentai but was rather timid to do so, presumably from public backlash on these forums.