A worrisome argument I recently read about the I Amendment establishment clause (Congress shall make no law establishing religion, or prohibiting the free exercise thereof) is that because atheism is not a religion by its own claim, nothing prohibits Government from enacting regulations about it, or against it.
I guess Wicca is safe (not) but if such an argument were to gain currency, I can see some trying to outlaw atheism. Not suppress it or belittle it, but outlaw it.
"Be ye not lost amongst Precept of Order." - Book of Uterus, 1:5, "Principia Discordia, or How I Found Goddess and What I Did to Her When I Found Her."