Cancelling fiduciary excuses

In trust relationships, one person has a 'beneficial interest' in another's performance. The former not only would but should benefit from the latter's action, and the latter has a 'fiduciary duty' toward the former to so act. But where that act would otherwise be wrong, the first person's beneficial interest would be providing a pro tanto reason for the second person to do something that is pro tanto wrong. That reason can – and should – be removed by the former renouncing their beneficial interest in the latter's pro tanto wrongful action. Doing so would cancel the fiduciary's excuse for wrongdoing on the beneficiary's behalf.