In the quoted statement, only one of those statements--"defying the laws of physics"--is perhaps beyond the purview of the military. We don't allow aircraft to willy-nilly cross borders, and neither does any other country in the world. (Border crossing is obviously permitted, but there are procedures and rules to follow. International incidents can arise when they aren't.) Also, using the example of deploying a nuclear device may be cliche, but what about a conventional weapon? Should there be any less concern about an unregulated aircraft capable of dropping explosive ordinance?
At a fundamental level, any military is tasked with guarding the land its sovereign occupies. You can't blame them for being careful because there's always the small, remote chance that an adversarial, human government could inflict harm if the military isn't looking. But that's precisely it: no one knows where these craft come from. Based on the hard information available to us the public, it's equally possible that the craft came from another galaxy, Mars, Russia, or Canada. We just don't know, and we can't just sit back and watch because there may be a legitimate threat.
At a fundamental level, any military is tasked with guarding the land its sovereign occupies. You can't blame them for being careful because there's always the small, remote chance that an adversarial, human government could inflict harm if the military isn't looking. But that's precisely it: no one knows where these craft come from. Based on the hard information available to us the public, it's equally possible that the craft came from another galaxy, Mars, Russia, or Canada. We just don't know, and we can't just sit back and watch because there may be a legitimate threat.