Replace Alien abduction by demonic visitation or ghost visitation. Same reasoning : you are making the classic error of dismissing the potential situation in which "of *ALL* being mundane".
Your null should be that all alien abduction are mundane, but are not recognized as such by the people living thru them, and can have a variety of explanation (sleep paralysis, made up memory thru hypnosis, just plain lying, psychosis, hallucination, brain clot, cancer, etc...etc...). It is up to you the CLAIMANT, to demonstrate that the null is invalid and that some of them have *evidence* that this was a real alien visitation.
But that is not what you are doing, you are doing a classic argument by incredulity "so many people can't be wrong !". You can use that for a variety of things. Like "from many people doing autodafé/hanging with witches they can't have been all innocent women, some must have been true witch !". And otehr various argument by incredulity.
That is a downright stupid argumentation and fallacious.