We already know that this is not the case; vide: Robosigning, the pushing of no-doc loans, the very existence of NINJA loans and the collusion of CDO packagers and the ratings agencies that has been amply documented.
The fact that not only have there not been high-profile prosecutions of the executives who created the conditions under which their employees engaged in systematic fraud; but the USDOJ has been actively coercing state AG's into agreeing to a thoroughgoing amnesty that will absolve most of the major players of any criminal liability. And pray tell, why would these bankers be demanding immunity from prosecution if they were not fearful that a serious investigation into their behaviour would find them guilty of, at the very least, criminal negligence if not outright fraud?
And that, my friend, is the point where you have to accept that the system is in fact broken; and that the checks and balances have been short-circuited; that the system is out of control and that we are fiscal flotsam on the tide of events from here on out.