Why do Christians think Pagans are Satan Worshipers when they are not?

First, I am an Atheist. But I hate seeing my Pagan friends get berated and treated so terribly because Christians think Paganism means Satanism. Hello out there Christians? Pagans do not believe in a Christian God nor a Christian deity like Satan. In fact they don't even believe Satan exists. Pagans are simply people whose religion is base in or around nature. Just like the Native American beliefs. I am part Native American and even though I am Atheist, I find the spiritual explanations of the Native Americans to be beautiful. So why do Christians continue to Satanize pagans? (By the way, the pentacle only refers to reverence for water, earth, fire, air and spirit. What say you?