Originally written for Quora as the answer to:
You are entitled to think whatever you want.
Challenge yourself to imagine something absolutely repulsive, the worst perversion possible - now keep such pictures pending in your mind and wait for the police.
Nobody came. How strange, isn't it? Your neighbor still says hello seeing you on the street, mothers do not protect their children in your proximity, and your friends do not hang up on you, ending dramatically mutual relationship.
Why is that?
Because nobody can peek inside your head to judge or blame you. And while you keep your thoughts private, meaning not taking actions towards 17 years old or younger girls, you are free to imagine them under any circumstances you find appealing.
To digress, how often have you heard someone expressing his wish to kill pedantic boss, idiotic politician, or hysteric wife? Saying so, he did not only show intent to commit a crime, he even didn't hesitate to announce such atrocity being amongst other people - yet hearing that, bystanders never bother to call police, sometimes even nodding in approval of such socially unacceptable behavior.
For some reason, your co-workers would not mind you murdering annoying boss in hypothetical scenario, thus, not harming him at all. On the other hand, you hardly receive encouraging responses if you describe explicitly sexual fantasies about cute teen daughter of the very same boss, especially if other women were present.
To cut it off short, sexual fantasies about under-aged girls are more taboo than violent dreams about rightful punishment of obnoxious manager. In the end, no harm is done. Unless, of course, you believe in Hollywood movies in which suppressed sexual desires, expressed in naughty drawing or talking, creates mere foreplay for becoming serial rapist.
In real world, however, inner and outer realms of our existence influence each other rather indirectly. Understand, mental scenes with beautiful girls forced into submission rarely push men into realization of these. Twenty years ago, men has been crafting models of trains or airplanes to release their accumulated erotic pressure. Today is more common to watch a porn.
Keep thinking whatever you want.