Technically it is an opposite of a fan. Not that that really changes your point. I believe I smiled because of the absurdity. Perhaps because I had just been reminded of the world of Calvin and Hobbes. The person in the strip has a fantastic idea which is then shot down by a stupid pun by a talking windmill. Could be that partial reason for the smile is the appearance of the windmill itself, as windmills have made several appearances in xkcd in different contexts.
But yes, you disliked it, I enjoyed it, XKCD hopefully goes on.