When did he get anyone to make a deal with him? I don’t remember it. From what I remember they come to him or summon him. It’s not like he’s chasing them around the Fairyland to force into something.
The fact that they are desperate doesn’t exempt them from responsibilty for the choices they make. They are informed about the cost, whether high or not, and they can always say no. When they are about to get what they want, they don’t seem to be interested so much in the other end of the deal. The realization comes later and suddenly it turns out that someone else ruined their lives. I sense some hypocrisy in that line of thinking.