I'd point out that we'd grown.
There once was a point where the wiping out of a species would be something we'd not bat an eyelid at. But these days, there are organizations and policies dedicated to keeping every species alive. We see it as a sign of our growing enlightenment as a species.
Therefore, if we are less enlightened than this alien species, surely we too should be kept alive, under these same principles of enlightenment.
And, if we are more enlightened, then shouldn't they reconsider the idea of wiping us out?