I'd say that this is a dangerous kind of piece to do, because it sets up Narrator Persona challenges, more specifically the Asshole Problem. I'm sure you guys have seen it--it's death if the biggest sense the reader gets from a critical essay is that the narrator's a very critical person, or from a comic essay that the narrator's cruel or snooty. Hence the importance of being just as critical about oneself as one is about the stuff/people one's being critical of.