I have absolutely no textual evidence for it, but it works for me! Merlin being the butt of the knights' humor kind of discomfits me, but I do love the idea of Arthur setting it all up as way to get back at Merlin for humiliating him in front of his councilors. Arthur did seem awfully pissy when he ate the last spoonful of stew in front of Merlin, then seemed to chill out a bit (depending on whether we see his praise of Merlin's cooking the next night as sarcastic or not -- with Arthur it can be hard to tell!)

Mmm, head canon!