Excellent post. A few comments:
Although there is no scientific evidence that fantasizing about kids causes pedophiles to molest children, an individual pedophile should attend carefully to his own fantasies. If he feels it increases his danger, he should take that seriously. Science never showed that there cannot be such a relationship for some people.
Next, it always helps to understand why opponents have different opinions. The reason many professionals and laypeople believe that fantasies lead to sexual offending is that the only pedophiles they have heard about are sex offenders. They see the end result (abusing children) and something that came before (sexual fantasizing) and really have no knowledge at all about the great number of pedophiles who had those fantasies and never abused kids. You also expect that the offenders, who are eager to show that they have a plan for not offending again, will suggest concrete steps they can take that they claim will be effective — such as not fantasizing sexually about kids. Professionals need to expand their thinking to account for the non-offending pedophiles they have never met.
Next, some people do think that an ordinary guy fantasizing sexually about a woman, even in private and later, is some sort of violation of her. I certainly don’t, but it isn’t obvious to lots of people.
Finally, exactly which sins God will forgive and under what circumstances seems like it may vary from religion to religion, and from sect to sect within Christianity. I wouldn’t assume that all would view adults and children the same with regard to being objects of fantasy.
All that said, I agree with your main arguments and conclusion. Most pedophiles should be free to fantasizing sexually about children, and the public at large should accept that we will.