Ok I'll try and explain better.. When snakes are eaten people intentional don't eat the part that can kill them.."if something is poisonous, that carries the thought you need to eat it in order for it to harm you. Rattlesnakes are eaten quite commonly"... Last time I checked if you were to ingest snake venom it runs the same risk of dieing from the venom.
Hence the "heads get cut off before the snake is cooked or eaten?"
So to say "Snakes are venomous, meaning they need to bite/sting you to do harm." is wrong the delivery method doesn't matter regardless of how the toxin gets into the body it is still harmful..Meaning it is still poisonous to the Human condition. All the toxin has to do is get in to the blood stream.. There are "Venomous" snakes that don't have to "Bite" you to do this. Spitting cobra's and stiletto snakes come to mind..