I would explain that if they keep threatening you to believe then you won't be able to have the true belief they want you to. Explain to them that you can't come to your own conclusion if they are extorting their beliefs upon you, which is what relgious beliefs should be all about. If that doesn't work, just fake it until you're old enough to tell them the truth.
Even if the open windows of science at first make us shiver after the cozy indoor warmth of traditional humanizing myths, in the end the fresh air brings vigor, and the great spaces have a splendor of their own - Bertrand Russell
