You share that hypothesis with a popular award-winning SF trilogy. My critique of that trilogy is that it doesn't incorporate the concept of present discounted value, which seems to derive from the apparently-universal laws of thermodynamics. If you have the power to destroy nascent interstellar civilizations, and the threat posed by those is their potential to use scarce resources in future, why spend the resources to destroy them now? How do you know they'll live long enough to use those resources? How do you know you'll live long enough to care?

All the predators we've observed, eat their prey to sate a present (or in the case of hibernators, near-future) hunger. We've recently learned how common planets and suns like ours are. Why would any hungry alien civilization drive past all those resources to get to us? We haven't developed anything particularly tasty yet...