It would be a fallacy to assume that every secret abusive program has a whistle blower, just because every secret abusive program we know about has had a whistleblower. It's like saying "there's no such thing as the perfect crime". Well, maybe, but if there were, we wouldn't know about it.
I agree, but my theory is that any mass surveillance program will necessarily employ a quantity of highly educated and intelligent people. People capable of interpreting the 4th Amendment for themselves and responding ethically, as the existing whistleblowers have done.
