In my opinion, the alien in the right pulled a fast one. He set up a joke. When the left alien asked if he thought a debate would be fun, the right one said “in my opinion.”

It doubles as both an affirmative—“yes it would be fun”—and as an inconsequential opinion which is the start of an argument or debate.

That’s why the alien on the left points at the other. As if to say “ah I see what you did there!”

Edit: ah notice the little smile and the sneaky squinting eyes on the alien to the right in the final panel. So smug that he made a funny 😆