Meh, I don't think it's entirely insane. I mean, let's be honest, if humans had the technology to cross between solar systems in a reasonable amount of time, you know damn well humans would be fucking with whatever relatively primitive civilizations they come across. Like, you seriously expect me to believe that the idea that there might be alien teenagers (or god forbid, adults) who might take a starship for a joyride and probe a bunch of hillbillys is that insane? We live on a planet full of people who'd do it for shits and giggles. Hell, maybe they probe buttholes because some closeted gay farmer was like, "mah butt's bleedin' 'cuz a buncha aliens dun probed it I swear, not 'cuz I tried to stick a socket wrench up there" and they found it funny and rolled with it.

Imo the insane part is the belief that they'd try to communicate through crop circles or probe buttholes to study the human body. Not that they'd fly around trolling humans.

Edit: maybe they're baffled by humans because every time they try to take X-rays and do an MRI to study the human body, the human starts screaming about probing anuses. The translator fucks up and suggests the human is asking for something to be inserted into their anus. Sure enough, as soon as the metal is inserted, the human stops screaming. Before you know it, they declare that the proper procedure for studying humans is to insert a probe before proceeding with the study. They're still trying to figure out why though.

That's why they have to probe so many humans. They only needed to abduct two or three humans to understand how our bodies work, but they're completely baffled and still trying to figure out what circuitry in the brain is responsible for the "anal pacifier response".

Edit 2: fuck, now I'm trying to think of legitimate reasons why an alien would probe someone's butthole. Assuming aliens are indeed flying around probing people's buttholes, the only two things I can come up with is A) they're trying to get samples of human gut flora either so they can understand the risks associated with it being introduced into a foreign (i.e. extraterrestrial) environment or because they've been using it as a bioweapon, and/or B) they're trying to provoke a vagovagal syncope as a form of natural anesthesia.