The non poisonous snake should also imitate like biting some one ! (Only for the sake of self-defence) Regardless of whether the snake has Poisson or not the hissing of snake will create the terror in the other's mind.
There is one small story regarding this. Once a poisonous snake used to bite many people passing by the way. When Shri. Shankaracharya came to know this he advised the snake not to bite people and trouble them. After few months when Shri. Shankaracharya was passing by the same way he noticed that the snake had become very much weak and had many wounds.
"What's the matter? Why have you become like this?", asked the great seer. It replied, "Oh Master! You only had told me not to bite the people. So when people came to know that I do not cause any harm they started pelting stones at me". Shri. Shankaracharya replied, "I had only told you not to bite the people. But I didn't tell you that you should stop hissing at the others!!"
It is said that a 'yogi' should not loose his temper and should be above all the emotions. Then how should a 'yogi' react to the wrong/ill things that people may commit around him? It's perfectly like the nonpoisonous snake above!! He should 'hiss' but should not cause any harm to others.
Probably the resourceful people ('Gunvaan' is the exact samskrit word) have to take many troubles while the unresourceful people live peacefully. Like a parrot lives in a cage while a crow flies freely in the sky!! (Sometimes the good qualities of a person may invite trouble to him)