Hanging or castration?
Not being an expert I would recomend a quick bullet to the head , but thats just me.
Is this perversion curable? Thats one thing, the other thing is has this individual moved from fantasy to reality , thats another thing.
Thus far ,as far as we know ,he has not , but not withstanding his human rights etc etc and bleeding heart ,liberal ,tree hugging ethics perhaps to be on the safe side,option three?
Do thought crimes become real crimes? no idea , don,t care ,as they said in Vietnam,kill them all let God sort them out.