A friend of mine did an internship. She was very happy and kept saying how great everything is, the job, the working atmosphere and the boss. Recently she told me that the guy never paid her for the 3 months work. She was a bit annoyed, but still completely under his charm and saying what a great guy he is etc…

I personally find swindlers (lets call them by their real name here, though my friend may not talk to me again if I dared connect this noun with her boss) repulsive. 

They are all charm and attention; they are sleazy, greasy creatures who use their culture/knowledge/looks to get benefits from their surroundings. They gain the trust, respect and sometimes even admiration from their fellows and use it for their own benefit. It's hard to put the finger precisely on what I dislike, maybe it is simply the fact that they are not nice/charming because they truly are so, but how they use their charm (or what is considered by most a charming behavior) in order to swindle people in different ways. I could see the swindler her boss a mile away, and could have foretold she wouldn't get paid, but she was (and still is) totally under his charm. Later I heard from other students that were employed there that he never paid them either, so this is a recurrent behavior. 

I urged my friend to let people know about the facts, at least so that the next students who intern there, may be aware of the possibility that they are working for free, but she wouldn't hear of it. 

 I have two questions: What is this charm of swindlers that makes people who were used by them, still want to protect them? And how should I convince my friend to denounce him, or should I?

The other thing that I thought could be fun: describe your favorite swindler.