theory: a nervous/insecure guy might hit on a woman when she's alone, because there's no-one else to witness his potential embarassing failure.

If my theory is correct, the guy will be too worried about his own pride to be thinking from the woman's point of view, so he won't realize that she could feel threatened. But that insecure guy is not much of a threat either.

The problem is distinguishing between the insecure clueless guy, and the potential rapist who also seeks a woman alone.