"Oh, you must have confidence."

I've been looking for a moral lesson in Herman Melville's The Confidence-Man, or at least some way to properly understand the book, but so far I am simply confused. The confidence-man, who may or may not be the devil (according to copious notes in the Norton Critical Edition of this text), spends most of his time convincing misers, misanthropes, and other con men to gain "confidence" in others, and when they are ultimately convinced, he uses their new-found confidence to steal their money. Is this loss of economic wealth a punishment for faithlessness, or is it proof, for the miser and the suspicious barber, that they should never trust men (especially with their money)? The confidence-man, moreover, does not manage to get any money from his fellow con man, Charlie, but simply thwarts his companion's own attempts to swindle. The book seems to simultaneously attempt to increase its readers' "confidence" and advance a sort of misanthropy itself. Whom shall we trust, and why? What does Melville want us to believe?