It's reprehensible but if they're not really acting on it, as in harming someone else (masturbation, really?), then why should it be a crime and the state be involved? What are you suggesting is that the mere thought of it, involving fictional people at that, should be a crime. Are we certain we want thoughtcrime?
That sort of vilification only makes them more likely to hide instead of seeking professional help. Why would they, if doing so would open them to ostracization?