The tomato plants are toxic, naturally toxic regardless of pesticides or organic farming like tobacco. Toxins can not be flushed out of the hornworms. If you get wild ones and feed them something else they will still have whatever toxins they got from the tomato plants they ate. Tomato plants are solonaceous which I believe are related to deadly nightshade.
About the only part of the tomato plant which is not toxic is the tomato itself. Worms which have never been fed solonaceous plants are the only ones that should be used.
If by staple you mean a regular feeder, then they are okay to use as opposed to the only feeder. The reason some people do not use them regularly is a matter of cost not suitablity.
Digby Rigby _______________________