@anon763: I get your point, and I'm warning right now (just to be sure, don't worry, there is no animosity here): I won't start a debate.
So, to answer your questions, even if you don't do a crime, planning to do a crime is, well, also a crime. Of course, we can say that he only tought about it and it doesn't mean he will actually do it, but the guy seems to be ready to act, and when you read his toughts, he seems to take way too much pleasure in the fact that it will make suffer his victim, hence why I said he seems dangerous, and why I say he "must" get arrested before he can do anything. (I mean seriously, freedom is one thing, but it's not normal to think about molesting someone. )
That's why I was talking about "karmic" retribution in my first post: the author showed us that there is some creepy person wanting to molest girl in a bus, and with some fucked up reason behind that. It would be really horrible if this "arc" end without a conclusion where we know the would be molester won't be able to molest anyone today or any other day.