Well, first, I'd check to make sure this isn't some desperate sweeps-week attempt to bolster ratings (Any who have seen South Park know what I'm talking about)
After that, I'd basically ask them why they want to destroy us. If it's cuz we're on land/resources they want, can't exactly fight them on that, since we've been doing that to every other creature on this planet since our creation. If it's cuz they think we're a plague, but they don't want our planet, just put a couple of flying saucers in orbit to destroy any attempts of us leaving. But make sure to let us all know first. If we fight back, please feel free to unleash doom upon us, but just try not to kill those who don't fight back, cuz those of us who refuse to fight will later worship you. I don't care what kind of species you are, NO ONE could want to kill an inferior species willing to kiss your anal cavity and/or mobility appendages for survival.