Blowing the whistle is an act of reporting misconduct or illegal activity to authorities. However, the antonyms of "blow whistle on" include withholding information, covering up, concealing, protecting, and keeping secrets. All of these actions can be detrimental to the welfare of individuals and organizations. Keeping quiet about wrongful actions enables them to continue, and can result in harm to individuals or the community at large. As such, it is essential to promote honesty and integrity, and encourage people to speak out against wrongdoing instead of protecting those who violate the law or betray trust.