To be honest, I find the entire current legal system sickening. It allows guys like him to weasel out of their mistakes. I am aware that collection companies step on toes, but it's necessary, or nobody would pay up. However, it doesn't justify letting this guy turn around and sue their asses for whatever amount he is.
It's like robbing a bank. You get off with a few million, say, but the police get you. However, they didn't read you your rights, so you can take the fight to the courts. Most often you'll win, despite being the proven criminal. It's very similar.