One argument in favor of it is intuition. Looking at pictures of forbidden things might reasonably make it more likely you'd do those things. There is resistance in many quarters to applying this reasoning to the parallel situations of fictional violence in movies and to the degradation of women in pornography, in part because there is no convincing data.

If you care about the issue you are pushing, don't make assertions like that without linking to relevant meta studies.

I might appear to have a vested interest in the availability of such materials. I don't, personally, though the number of men who are given years in prison for looking at pictures does distress me deeply.

Motivated reasoning doesn't score you points on Lesswrong. In a case like that you would profit from keeping your language as academic as possible.

It might be okay to make a joke about suffering that those men who are imprisoned face but making jokes in contexts like this isn't easy so I wouldn't recommend you to try.

In any case, one of the rationality principles does say that arguments should be evaluated on their own merits, not the attributes of the person making them.

You yourself say that you are in the emotion of distress that indicates that you aren't thinking clearly about the issue and it helps people to draw conclusions about your argument.

A reasonable analogy might be sex education. Some conservatives oppose it because they think it will make kids (teens especially) think about sex and become sexually active. The data doesn't support that, of course, and the explanation is that kids are thinking about sex already. Pedophiles are also thinking about sex; the fact that the people they are attracted to are always inappropriate partners doesn't change this aspect of the situation.

If that analogy is correct there little we can do with regards to pedophiles besides locking them up. Cyberporn legislation would be a tool to do so.

Besides you fail to provide any reason why this analogy should hold. Shall we believe that being a pedophile is genetic and the enviroment to which a person is exposed has nothing to do with them becoming a pedophile?

I believe one major objection to all forms, including the virtual, is rarely formulated: people find it gross and disgusting.

The fact that you think it's rarely formulated says more about you than about the position against which you are arguing. There are plenty of people who do consider all forms of pornography to go against human dignity and to objective the objects that pornography shows.

Even if that doesn't bother someone, the alternative of virtual child pornography should be tried first.

That leaves the question of how to decide if a given image is virtual or isn't.

Non-consequentialists don't want to sacrifice the welfare of a few children to help the many.

That no sentence that you should write in a context like. It raises emotions that you don't want to get raised.

You also haven't identified what welfare you care about. Is it about the pleasure of consuming child pornography? If so, is it basically about providing a way for pedophiles to wirehead themselves? If that isn't the goal what is?

You also muddle your goal. You start by pretending that you just want a discussion about whether child porn availability increases child sex abuse and end by calling for legal changes.

PS: Lean to format your links correctly. Not knowing how to format links signals your outsider status.