I'm finding it hard to find fault with your argument. I think where our differences lie is that I don't believe its a moral imperative for someone to risk their

I'm finding it hard to find fault with your argument. I think where our differences lie is that I don't believe its a moral imperative for someone to risk their livelihood to whistle-blow against something that is fundamentally someone else's responsibility. If the janitor at an investment bank overhears fraud being discussed, I don't believe the janitor has a moral responsibility to expose that fraud if it risks his own livelihood. Similarly for a teacher who puts in a commendable effort to weed out cheaters only to be essentially punished for it by the administration. It's his job to make note of cheaters, but the responsibility for doling out consequences is a cooperative effort between the professor and the administration. If the administration isn't doing their job, and exposing this risks his own career and livelihood (for a professor publicly going against his administrations this might actually be the case), I don't think he has this responsibility.