My husband was a pedophile, in much the same way anyway. He had never once acted on any of it, but he too believed (and imagined) that it would be possible to have free love with a child. He knew the thought was incorrect, and incorrect to have, but nonetheless, it was there in his head and he couldn't do anything about it.
He struggles with it at least a few times a year.
Honestly, though, i have to say that I would not crucify you - but be tender on the approach of the topic. Private place, preface with all the right terms like - I would never, ... I know its wrong... but the thought plagues me anyway, etc. It's called having intrusive thoughts when the thought keeps coming back over and over even though you deny the thought as having any merit.