You definitely need "there are no rules" at first, but when your protege starts belting out Wonderwall in his best Bob Dylan impression, you have to switch to "there are some rules."

Where I live, if you order a random taco off of a delivery service (I know, I know, I've pretty much stopped), you have a decent chance of your "taco" being on a fajita shell and containing iceberg lettuce, with a packet of mass-produced hot sauce on the side if you're feeling adventurous. I think the weird absolutist positions well-meaning americans take is in response to this sort of disrespect for the history, the person making the food, the person delivering the food and the person eating the food.