In the Garden of Eden there was no evil before Eve ate of the tree as it is believed by some, assuming that the snake knew not to eat the forbidden fruit would it not be considered evil for him to tell eve to eat it?
You got to be fucking kidding me....
IMO it is not, the snake just discloses the human condition. The 'evil' in this world is nothing else than us refusing to be what we truly are. The snake is the representation of this human tendency. Whether you call that tendency evil or not doesn't matter in the end. It's there and somehow we have to overcome it to be able to get back into paradise.