Or should one give up ? Often, after blowing the whistle, the powers that be deal with the problem, but in a way that does not really punish the offender, nor prevent him from continuing his/her behavior. The whistle-blower is often left frustrated by the method chosen to deal with the situation. Letting someone go instead of firing them, moving a child molester to another location or job instead of total public disclosure and prosecution.
And yet, examples of exageration abound on both sides. The whistle-blower who makes it a personal crusade and is never satisfied with the punishment. The offender who goes on to another position and keeps transgressing... Hard to come up with a black and white decision on many of these issues. Ethics is often just dealing with the grey zones.