Not true. Some snakes are docile by nature, whereas others will strike at almost anything. My daughter has a 4 ft. ball python that is sweet as pie.
OTOH, I once had a yellow rat snake that was the meanest critter you could imagine. It would strike at the glass in the cage if you came anywhere near it, and absolutely could not be handled without biting. It had nothing to do with whether or not he was hungry. Some snakes are just way more aggressive than others.