I've come across a comment almost exactly like this before on HN; was it you who posted it? Zizek does entertain, but most popular writers also entertain, and entertainment is not mutually exclusive with philosophy. He is respected within philosophy (and Chomsky is not a philosopher, as much respect I have for him too) and widely cited. The inversion of common sense things is precisely the aim of critical theory. Granted, Zizek draws from "low culture" too in order to appeal with popular media, but you can't simply say he's
not a philosopher. What he does is philosophy or critique of it and you can read as much in his books.
You might say that he lacks rigor or prowess in his arguments, but those admit he's a philosopher. I can't see how you can deny he is a philosopher. Let's rephrase the essence of your argument: anyone who writes to entertain or repeatedly questions notions of common sense cannot possibly be a philosopher (despite large output and several research and teaching positions in and invitations to philosophy departments at universities around the world), if and only if a linguist says so and they have a lisp and some nervous tics.
I'd also suppose that none of the topics which Zizek addresses are philosophical ones: https://www.iep.utm.edu/zizek/
