It's the point I made--it is not at all difficult to make an argument that we have not been visited by aliens.

> we might have been visited in forms that are completely incomprehensible to us

So what? That's not an argument that we have been. It's not a rebuttal to the arguments that we haven't been. It's like saying that President Trump might be a shapeshifting reptile from Aldebaran. "It MIGHT be, so it's difficult to argue to the contrary"--wrong. It's like saying to someone who notes that there's no elephant in their dining room that there might be one that's invisible and very nimble so no one bumps into it--"it's difficult to argue otherwise"--wrong. It's a child's (or theist's) "anything is possible" logic. It's hypocritical because no one uses this sort of nonsense outside of such special pleading--imagine a lawyer for a mass murderer with hundreds of witnesses telling a jury that actually it was done by aliens with incomprehensible technology who created the illusion that it was their client who did it--"it's difficult to argue otherwise"--wrong. This sort of "might have been" garbage has no place in rational good faith discussion.