I could not find articles specifically addressing the situation you describe. However there are lots of articles giving evidence that interest in child pornagraphy tends to correlate with actual child molestation. Here's an example: https://www.mentalhelp.net/blogs/chi...al-pedophilia/

Does the father currently have visitation rights, and what are the terms now? Would allowing unsupervised visitation be a change from the current situation?

You have to ask what goal is going to be helped by unsupervised visits? Then one has to ask if the goal is a fantasy-wish. I've heard things like, "I want my child to have a father." and "I want that relationship to be as normal as possible." Sometimes, no father is better than a bad father. Sometimes, a father is not capable of interacting in a healthy way.

Sometimes a parent thinks that the spouse has to be expected to help with parenting, as in: "This is his kid too." If one parent cannot be trusted to act in the child's best interests, then the responsible parent has to assume full responsibility for parenting. No parent can ever rightly say: "I'm only responsible for 50% of this child's parenting needs."

There's more cause for concern than just the risk of these children being sexually molested. An adult who is interested in child pornography probably has other issues of deficient morality.