Making the assumption* that some decent fraction of those who consume such media would be sated if they could get it and not move on to actually hurting children. Then couldn't a preventative measure be to take all the existing child porn and make it available to them?
Though I guess that risks normalizing the condition and could lead to it being more commonplace (certainly it would appear so as those who successfully suppress it would hide it less) and if it's more commonplace than the fraction that does still act harmfully upon the impulse could, in absolute numbers, exceed those that do today. Figuring out how things fall would first require a good understanding of the numbers.
*I don't know if this is true or false and would be interested to know if there is existing general consensus on the evolution of seeking out fantasy fulfillment over time in general and how it's affected by free access v. restricted access to related material.