Bad Thing Is Right

''Huh. So the wrong thing to do was the right thing to do the whole time. Looks like I've been living life wrong!''

When somebody is doing something that is considered the wrong thing to do, then that action suddenly becomes what they have to do, often to Save The Day. At first, this person might have some reason to not do the wrong thing after being told it's bad, but they eventually find a way to do what they now must.