Suppose that's true. Does that mean that sharing of child pornography increases the incidence of child abuse itself? I would argue probably not, or at least that the increase is fairly small compared to the resources that go into combating it. Public forums do encourage sharing, but that doesn't mean that what's being shared wouldn't have been done in the absence of the forum. It just wouldn't have been shared.
The main questions that need to be answered are these:
1. Does viewing child pornography actually encourage child abuse?
2. Does viewing child pornography discourage child abuse by giving pedophiles a sexual outlet that doesn't involve harming additional children.
3. How much more does it cost to catch and prosecute someone who produces CP than someone who merely views it?
It seems likely to me that, at best, we're wasting a lot of money reducing a factor that has a small negative impact on actual child welfare (people who view child pornography), when that money would be better directed at a factor that has a much larger negative impact (people who abuse children). At worst, we may be spending money going after a part of the problem which actually mitigates harm.
Whether or not it is the latter is unfortunately a very difficult question to answer. Most common wisdom about "sexual repression" and "outlets" is pretty much without scientific basis, as is the opposite wisdom that pornography encourages sexual behavior. The one correlation that can be drawn is that the results of studies on these matters tend to align strongly with the politics of their authors.
But in any case, yes I think it's safe to say that the focus specifically on pornography is wasted effort.