I agree with your point but they are not the same thing. If you drank venom, nothing would happen. Same if you injected poison. Venom attacks the nervous system through the circulatory system, usually breaking down blood cells and such. When poison is ingested it attacks the body usually through the organs. I feel the need to argue the point because as well as being in to reptiles I am also an English teacher. Snake venom is venomous to humans. It is not poisonous to us. People do use certain words interchangeably sometimes but it doesn't mean it is correct and tends to drives me nuts as well.