I think that's his point. If they're not there, they're not able to be collaterally damaged. If there is intelligent life (or, any life as we define it genera

I think that's his point. If they're not there, they're not able to be collaterally damaged. If there is intelligent life (or, any life as we define it generally), there's a pretty high likelihood our arrival could damage it, especially if we don't discover it until after arrival. (And "really especially" if we go the terraforming route)