The Bible was many times translated,changing in time, which makes it highly likely that there are misinterpretations in it. The symbol of the snake has had many meanings to it. Originaly, it is said that it represented the waters. Later it is a symbol of Energy and Kundalini. How did it become a symbol of evil? Is it because people used the energy to do evil things ? Then the snake can be both, knowledge and evil.
A wise man has the snake under control...a Master