Will Regular Gas Hurt Your MINI Cooper S?

Car Talk's Tom and Ray tell writer Howard that using regular unleaded 87 Octane gasoline won't hurt his MINI Cooper S since premium gasoline is only recommended in the owner's manual.  Tom concludes:

So, for your own mental health, I suggest that you forget this whole incident ever happened. If you have trouble letting it go, I suggest going to see your Mini dealer's in-house hypnotist. He's conveniently stationed next to the cashier at the service department's pick-up window.

So, you MINI Service people tell us. Are Click and Clack, the Tappet Bros., right or wrong?