I didn't miss this point, I just reject it.
Throughout my career I have seen and been faced with these sorts of difficult situations, but ultimately I and everyone else has had a very real choice:
Do what one knows is wrong to perserve one's job or change jobs and remove oneself from this perverse choice.
Teachers are uniquely succeptible to making the wrong choice because they have been (willingly) conditioned to believe that their job is sacrosanct and that they, personally, are more valuable than their profession.
Yes, if you back someone into a corner you should not be surprised when they rationalize any and all misdeeds, but this doesn't excuse them.
As a manager, you should never put your employees in such a position for the very reason that you cannot rely on their inate integrity, but this, by no means, suggests that the people who revert to the behavior of cornered rodents are innocent victims.