Human
Explanation
The Joke
Aliens have captured a "representative human" and are interrogating it for secrets about Earth. The human immediately starts spouting conspiracy theories: "The moon landing was fake! It was all a sound stage!" and "Earth is flat!" The aliens, initially excited, quickly realize that these "secrets" are not actual insider knowledge but just the ramblings of a conspiracy theorist.
One alien remarks to the other that "these creatures aren't a threat" because they cannot even reach their own moon, let alone pose a danger to an interstellar civilization. The other alien agrees, and they bid the human goodbye, having concluded that humanity is too ignorant and gullible to be worth worrying about.
The Humor
The comic imagines a first-contact scenario where, unfortunately, the "representative human" the aliens captured happens to be a conspiracy theorist. The irony is multilayered: the human thinks they are revealing shocking truths, but they are actually convincing the aliens that humanity is hopelessly primitive. The aliens' dismissal -- that humans cannot even get to their own moon -- is based on the human's own false claim that the moon landing was faked. So the conspiracy theorist has single-handedly set back humanity's reputation with an alien civilization, not by revealing real secrets, but by making humans look too foolish to take seriously.