There was an interesting discussion going on in the chat box about whether it is normal or not for people to think about certain things. Rape was the topic but I think this can be safely extended to other non-politically-correct issues. My take is that we all are capable of thinking that way but that such ideas are so embarrassing for people to admit in public that they deny any knowledge of them to save their faces. @point and @Kim claim that it's not normal for people to think that way and that anyone who does requires medical treatment. I was challenged to present evidence other than my opinion to back up my claims.

I'll begin with this:

Quote Originally Posted by Wikipedia - Intrusive thoughts
Many people experience the type of bad or unwanted thoughts that people with more troubling intrusive thoughts have, but most people can dismiss these thoughts. For most people, intrusive thoughts are a "fleeting annoyance."Psychologist Stanley Rachman presented a questionnaire to healthy college students and found that virtually all said they had these thoughts from time to time, including thoughts of sexual violence, sexual punishment, "unnatural" sex acts, painful sexual practices, blasphemous or obscene images, thoughts of harming elderly people or someone close to them, violence against animals or towards children, and impulsive or abusive outbursts or utterances. Such bad thoughts are universal among humans, and have "almost certainly always been a part of the human condition".
http://en.wikipedia.org/wiki/Intrusive_thoughts