They seem to date from back in the Meiji restoration period. But this is Japan which is also known for the Soaplands, so go figure.
Possessing digital/virtual information that required abuse endorses abuse. Entropy is our friend here; only an extremely rare set of bits results from child abuse. You won't just find it.
Even fiction or photoshop is illegal. Your argument is much more applicable here, but seeing how society treats even inactive pedophiles as criminals rather than sick, I don't think it'll be very popular.
So, like a violent (e.g. decapitation video) that nevertheless plays on all major outlets?
I'm not really sure what you mean here. What makes something being "digital" or "virtual" special? Isn't the content/message more important than the way it is stored and transmitted?
I mean, concretely, you really think if someone has an illegal picture on their computer, and you can prove they were aware of it, that should be treated differently than them having that same picture only printed?
If someone sends an email to hire an assassin, is the fact that it was a digital message so relevant?
...and I feel that is the root of the problem.
I'm against real pedophiles and child abuse as much as anyone, but it feels to me like possession of otherwise illegal digital or virtual information should really be decriminalised, simply due to its immensely malleable and interpretable nature. It reminds me of things like "illegal primes" and such. Moreover, people can already perform, in the virtual world of games, acts that would be highly illegal in the real world --- and yet this still remains legal.
Maybe after we get over the War on Drugs...