Two wrongs don’t make a right
An informal proverb used to discourage retaliation or reciprocation, in that a wrongful action is not a practical or morally appropriate way to correct or cancel a previous wrongful action. Many people, of course, believe the opposite, namely that “two wrongs make a right” which, of course. is normally fallacious, while its antithesis, "two wrongs don't make a right" is not. Both sayings depend ultimately upon one's ethical viewpoint, and both date from the early 1700s.