I wouldn’t get into a battle, because then, you’re making yourself, and I guess in grandma’s eyes, making atheists look even worse. I would just kindly ask her (if you feel it gets to that point) do you think I’m bad? Do you think that I’m evil? Why do people that don’t believe in god = something bad in your eyes? I wouldn’t really do that until you thought it was absolutely necessary though.
Anti-intellectualism has been a constant thread winding its way through our political and cultural life, nurtured by the false notion that democracy means that 'my ignorance is just as good as your knowledge.' -Isaac Asimov-