You made a good point.
I’ve though about this quite some time. And the core problem of all of this, is the intent.
Or rather that we can’t find out your intent.
If we knew the intent, we could put someone who is trying your scheme, into jail. But not someone who really accidentally landed on such a site. (E.g. a Goatse-like CP link going trough a URL shortener.)
This is a giant problem. Which results in the self-contradiction of:
1. Innocent until proven guilty. (= In case of unknown intention, you are not guilty.)
2. Ignorance is no protection against punishment. (= In case of unknown intention, you are guilty.)
I think (2) is morally wrong, because in the cane that the intention really is not known, one should never assume evil intentions. Ever.
That’s what proof is for! Proof of intention.
A) Someone downloads CP. He jacks off to it, and gets caught in mid-action. -> Guilty!
B) Someone downloads CP. He tries to analyze the images to see if he can find clues on how to catch the guy. Later, someone finds the images on his computer. -> NOT guilty! Even if the intention was not known. Even if his intention was bad, but not known.
A fair society demands the rules to be like this. Or else everybody can just shove CP on your computer when you don’t look, and then throw you in jail for it.
There's no future in time travel.