Tell them you have more productive things to do with your time than listen to a load of horseshit. Seriously, why should it be so hard for young people to tell their parents they don't believe in bullshit fairy tales?
Christianity: The belief that a cosmic Jewish Zombie who was his own father can make you live forever if you symbolically eat his flesh and telepathically tell him you accept him as your master, so he can remove an evil force from your soul that is present in humanity because a rib-woman was convinced by a talking snake to eat from a magical tree...