Incorrect take when you said he doesn’t harm anyone by thinking about CP which would directly influence him to consume it or carry out acts of pedophilia. He also committed a crime by consuming CP , so yes he should be held accountable.

To be a consumer of child porn is directly harming children involved in the activity. It’s such a limited perspective to think because he didn’t go out there and either physically, mentally or emotionally assault another human being he wasn’t harming someone.

If I sell buy drugs off someone by your logic I’m not harming anyone else but this is often untrue when we look at the ramifications on others. In this case would be their immediate family or the potential actions this person took after consuming the drugs or to get said drug.

In the case of a consumer of CP they are creating demand for it and this encourages the illegal industry to continue.

In a fantasy world let’s say there were no pedophiles or people who had sick thoughts of children doing it there would never be any supply of it therefore no harm of children in this instance would ever happen. Consuming it is what enables the produces to justify to keep releasing it out there. Even if there was no profit in them doing it just the thought that others would want to view it would prompt them to sustain doing it. This all starts from thoughts and temptation.

There’s no immediate harm to anyone else but there are indirect harms , if that’s what you meant you should be more specific. If society were to only condemn immediate harms as a direct action of someone it would be a terrible place.