I wish a technologically advanced species would threaten us with war. Just a threat, but a credible one.
They could just threaten to steer a medium sized asteroid at us, one hit and it could wipe out the human infection on the surface of our planet if it was big enough.
Mind you I'm just hoping for the threat to happen, no actual harm.
It could be the best thing to happen to humanity ever, as it might unite us, however briefly, with a common purpose.
Of course once the aliens went away it would be Jeebus as usual. With the killing, and the get the heretics, and the God Hates Nearly Everything.
But any aliens out there might be just as much religious nutcases as humans are, if not worse. Just consider the different races in the Halo universe.