Could it not be that realising the full implications of the energy crisis, as we have to, to consciously avoid extinction, also involves accepting the only fix, to go fully solar powered, and all of the systemic implications of that on economy ("Budgets", and many other conventional economic concepts become meaningless), and what we know about science, and even religion, and thus also what we know about extraterrestrial life, requires 100% alignment of our species, the opposite of the old divided profit driven world we have to leave behind, and we can't yet change the feudal nature of humanity, so we have to have a common enemy for now to focus on, in order to resolve the current differences amongst humanity, whether that extraterrestrial threat exists or not doesn't matter, the primary aim would be to unite, rather than divide.

I don't think real intelligent extraterrestrial life would have a problem with that, if it exists, it would be easily capable of defending itself against the worst we could throw at it, even playing along, or of educating us sufficiently when needed, to convince us that there is no threat. But the main thing achieved would be the unity needed to get rid of the profit driven divisive capitalist economy, which lets face it, is practiced by all of the worlds governments, and subsequently all people, we have to smash it by going fully solar powered, fully energyist, as seems to be the only truly sustainable option.

Bring on the big bad alien threat, it seems to me it can't do much harm, only good.

This is giving the Empire the benefit of the doubt, probably stretching credibility beyond what exists, but hey they can't be all bad, all of the time :)