Near one extreme, CP captures a child being penetrated vaginally or anally by an adult penis. When we consider the milder end, I would like to broaden the topic to include anything that someone might find erotic, and leave aside its legality -- something that varies over time and jurisdiction.
Some people are distressed that pedophiles might see a child and think erotic thoughts, or see innocent pictures online and entertain erotic fantasies.
But for something to be on the CP spectrum, the person taking the pictures or video has to have the intent to produce something arousing to a pedophile.
At the mildest end of this CP spectrum is posing for child modeling sites. While ostensibly a way to help aspiring children get exposure for a modeling career, the economic model is that pedophiles pay for access to a set of pictures and video. There is a strong impetus in society to shut down such sites, conflicting with a reluctance to infringe too much on freedom of expression. One argument against such sites is the same as the argument against virtual child pornography -- that it might incite pedophiles and lead to their harming real children. It is in my view <a serious infringement on free expression>, especially with no evidence of such a link.
But what about harm to the children? In my view, this is what should determine the legality of making and distributing such material, not what some pedophile might think while looking at it.
In some modeling sites, the children are doing nothing remotely sexual. In others, they may be in suggestive poses and/or wearing suggestive clothing. As I see it, a key factor here in judging whether this is morally wrong is whether this is behavior you would expect a child to engage in freely under normal conditions. For many girls, the answer is an emphatic yes. Many girls love dress-up, and striking suggestive poses is also natural. Girls play at the behavior of the adult women they will become, and for many that includes trying to look sexy. It is very hard for me to see the harm here. Of course it is possible that a particular girl was coerced into the activity, but once you allow such speculation, there are no limits . We can suspect parental pressure on child actors or performers of any sort. Has anyone else seen a 7-year-old child giving a violin recital and looking decidedly unhappy?
Moving past modeling, there is other activity that is natural for a child, such as masturbation. However, while common this activity is under normal circumstances private. This is where in my view capturing it on video and posting it crosses the line from moral to immoral. When this child grows up, he or she will rightly believe his or her privacy was violated. But when we think of how we want to punish a pedophile who looks at it, it doesn't quite fit the image of CP as children being horribly abused.
Children may be captured being caressed by adults, or stimulated sexually. They might be captured watching adults masturbate, or themselves masturbating or stimulating an adult or other child sexually. Making this sort of CP is wrong, because the child is doing something children do not choose to do of their own accord (along with being done in private and not something most people choose to post publicly). The child's real feelings here surely cover a range -- they might find it kind of fun, view it neutrally, or hate it. This would be imperfectly reflected in their visible reaction. Typically we would expect a child to look happier than they feel, but the opposite is possible. CP producers might instruct a child to act terrified or miserable.
Penetration of the child by a finger or small object is worse. And returning to where we started, penetration by an adult penis is worse and even farther beyond the range of what a child would freely choose. Anything that is explicitly meant to cause pain, fear, or humiliation is in my view worse and even more despicable. Making a child do anything near this end of the spectrum is terrible, capturing it on film is worse, and posting it for others to see even worse. But this extreme is a small minority of CP.
My main point is to remind people of the wide range of activity that would all fall under the label of "child pornography". For me, sexy clothing and posing is not morally problematic. We cross the line with behavior that children do not normally do with anyone watching.
Even with the morally wrong material, our feelings about a man who watches it may vary depending on what he is watching. A child who is masturbating and appearing to enjoy it is not the same as one who is being brutalized.