Can't say that's surprising to hear. In the time he's been here, he's gotten to learn first-hand that humans have all sorts of quaint little categories for things. They're all more or less interchangeable from the perspective of a monster, and yet there's still people who act all shocked when they realize that a skeleton like him and a dinosaur-lizard scientist like Alphys are the same species. That kinda variation just don't occur to 'em.

So he's honest. He can appreciate that, on top of everything else.

"Can't say I can really understand the point of it. But, uh, I guess I shouldn't be surprised." Monsters must'a been sufficiently different enough. Turns it all into an us vs. them, as the Doc said, and then - what? They move onto assigning the next them to drive away and divide?

"But you eventually reach a point where it ain't really feasible to divide anymore, y'know?" Can't divide by one, or divide by zero. Just don't work like that. Viruses, maybe, can compensate for high rates of division with high rates of population, but humans ain't viruses.

And for good reason.