Blowing up at a kid is only going to make it harder for them to approach you in the future. I highly recommend Kickiga's suggestion 
Besides... it really doesn't matter if 'your kid' ends up religious... they are still your child. Hating them over something so small as that is kinda lame

Besides... it really doesn't matter if 'your kid' ends up religious... they are still your child. Hating them over something so small as that is kinda lame

Please give me a home where cloud buffalo roam
Where the dear and the strangers can play
Where sometimes is heard a discouraging word
But the skies are not stormy all day