It's an unwanted opinion for sure, but that first thing is fair enough. Even though Papyrus is starting to feel awfully lonely and put out, wishing more of the Harbingers were on the same page with regard to theatrics and how much cruelty to inflict in their chaos and confusion... He's still not hanging out with Herbert. The doctor is no Jerry, but...

"Well," he says, casting about for a good retort and coming up empty. "Fine! Go ahead. I don't need you to believe. And I won't even tell you I told you so, because, we won't exist."

It kind of feels like losing an argument already, he doesn't want to be the one to stomp away... that'd be like losing two arguments. But does that really matter? Does any of this matter, when they're just going to erase it all?