Speaking as a Psych Major, there's an element of truth in what you say regarding child molesters and others with uncontrollable compulsions...but only an element. People, all people, can still choose, some choices are just more difficult than others. Some of them require work, a lot of it, and some people don't choose to break their patterns. Which can be either good or bad depending on the pattern in question. But everyone can do it if they have the strength of will and the motivation.
The FATE system, while by no means an accurate simulation of the human psyche, actually handles this fairly well, via the ability to refuse Compels but only at a cost. But that applies to everyone, not just people with diagnosed disorders or issues. People with those kinds of things just have 'Aspects' that result in more societally inappropriate compels, not necessarily less Fate Points to throw around.