Let me ask a view questions.
Is it clear that viewing child pornography is always wrong? Consider a detective who is viewing it in an attempt to establish the identities of the participants.
Is it clear that any photograph of children being sexually exploited by adults is ipso facto wrong? Consider a reporter who takes pictures of some politician in bed with a pre-pubescent boy.
What is distinctive of the case in which we would intuitively regard the viewing as wrong? What attitude towards the participants does such viewing involve? In particular, what attitude towards the children does it involve? Does viewing child pornography as a way of achieving sexual gratification seem compatible with a compassionate attitude towards children and a proper respect for their interests and their autonomy? Does it seem compatible with a proper appreciation of their suffering? The wrong might lie less in the viewing than it what one's viewing such things as a means of sexual gratification says about the person doing the viewing.
That said, these are questions about morals, and some of the questions raised strike me more as questions about law. And it's a different question whether possession of child pornography should have the sorts of legal consequences it does. Here, it seems to me that the legal justification has to be that possession of such material involves supporting the market for such material and thereby contributing to the exploitation of children. But one could agree with that and yet wonder whether some of the laws concerning child pornography are not overly broad. Not many years ago, a woman was arrested in Cambridge Massachusetts when she went to pick up some photographs that showed her husband playing with their naked toddler on the beach. The person who developed the photographs had notified the Cambridge Police Department and called them when she arrived.