it's a really sensible and common response to papyrus tbh. someday i should throw papyrus in the kitchen so rin can see the absolute travesty that is the cooking training the skeleton's been through. it might not help the idiot impression, but it can be loud and constructive

...you know in hindsight, with the headcanons me and quix are using for papyrus and sans, there's some funny parallels/contrasts to rin and yukio going on. the relatively loud and spirited and kinda-naive/idiot brother, vs the scientifically-minded one long keeping terrible secrets and more familiar with ways and reasons to kill. and lately a lot of family drama going on between them because of it.