How many times did you hear that gem? It often went along with "the truth is a protection" which is their way of saying "living a moral life is good for you ... and you can't do that without us".
But think about what people are really saying. I think the real message is "I know it's not the truth, but I chose to follow it anyway".
It seems like a pre-emptive argument because they know they can't defend it as "the truth" so instead they switch to defending it as a lifestyle.
Of course any kind of lifestyle that has a decent moral ingredient to it, respect for law and order, discipline etc... probably increases people's chances of doing better in life, but they don't have a monopoly on it.
So just remember, next time you hear someone saying "even if it's not the truth" what they are really admitting is that they already know it isn't.