"Snakes are Evil", some say. I wonder if this assumption has any connection with the book of Genesis.
Satan wasn't stupid when he chose to disguise himself as a snake (or serpent).
In order to fool Adam and Eve into eating from the Tree of Knowledge, he had to choose an animal that they found intriguing. Perhaps, at that time, it was one of the animals in the Garden which they admired most.
So, in my opinion, when people refer to the snake as being evil, they are merely continuing to fall for the oldest trick known to mankind.
Time to get educated people!