When for-profit colleges promise graduates jobs which they generally can't get, are the colleges guilty of fraud? Of false advertising? Or are they simply displaying their grasping nature?

There is no need to investigate precisely how bad for-profit colleges are, because there is no good reason for them to exist at all. The US government should stop offering aid to study in them. That would more or less get rid of them all. Traditional not-for-profit colleges would pick up the load.