Alien on the left is about to debate whether or not that would even be entertaining. The point of the comic is that debating our opinions with each other is stupid because they don’t matter and it’s not even fun.
That’s a really cynical read of what’s obviously a lighthearted joke.
The joke in the last panel is that the book alien is stuck in a paradox. if they choose to engage in this debate, they would have to take the contrary position that engaging in a debate would not be fun. But by engaging in the debate, they would actually negate that argument, because you still participated in the debate.
Calling your own personal interpretation obvious is pretty silly. Also, the entire comic is pretty cynical, but it’s also lighthearted…so to each their own. I overstated it in a rush to get ready for work and can acknowledge your view on that paradox, but I maintain that the overarching moral is that it is still pointless to debate that which amounts to personal opinion.