And if everyone is available for the right price, it doesn't make sense to have an entire category of "Untouchables". If the Rays offer Junior Caminero are you really going to say "I'm sorry, Francisco Lindor is untouchable". Of course not. It's just degrees of value.
As for Benge, like everyone else, I'm hoping he becomes great. And I'm encouraged by his progression. But he's not great yet, nor can we assume he will ever get there. Nick Markakis would be a great outcome for him. Benge's value, at this point, comes from the fact that he's young, controllable with upside. If an elite player becomes available, and Benge is the asking price, you have to listen.
Do I want to trade him? Absolutely not. But if he's the centerpiece of a trade for a superstar, then you trade him for the right price. Preston Wilson for Mike Piazza. Carlos Gomez for Johan Santana.