Two wrongs make a right
Conservative journalist Victor Lasky wrote in his book It Didn't Start With Watergate that while "two wrongs don't make a right", if a set of immoral things are done and left un-prosecuted, this creates a legal precedent. Thus, people who do the same wrongs in the future should rationally expect to get away as well. Lasky analogizes the situation between John F. Kennedy's wiretapping of Martin Luther King, Jr. (which lead to nothing) and Richard Nixon's actions in Watergate (which Nixon thought would also lead to nothing).