The characters you refer to as predatory and unsavory are useful. They're the ones who make a novel into a thriller. They're active, and most of the common virtues, the signs of a good person, are not.
Thomas PerryThere is no place so benighted and godforsaken that some moron won't go there on vacation. People could be living in an open sewer and swallowing dirt to stop the hunger, and there'd be a couple from Larchmont wearing comfortable shoes there to take pictures of them.
Thomas PerryBut at the same time, the commonplace statement about them is true: every character is the hero of his own story. Each has a justification for his actions that is convincing to him. It's fun to give these people voices.
Thomas Perry