No, seriously. The pizza isn't a metaphor for anything specific.
The scenario of someone going to complain about _____ at a place where people who like _____ congregate is inspired by a number of situations, and is something I thought of over a decade ago when "_____" would have been EGS itself, but this isn't meant to be limited to any one thing.
I wish it was limited to just one thing. We could live in a world in which this only happens with Star Wars, and we would pay tribute to George Lucas for attracting such arguments to that one corner of everything. Instead it happens in some form or another with pretty much anything one can have an opinion about, ranging from the relatively trivial to the serious.
I don't really like explaining this in the commentary, but I've got a few people after me for the secret of the pizza, and I want to be clear that there is no secret of the pizza.
(The actual secret of the pizza is it would have been bagels had I not thought of more things that could be said about pizza)
(Because I like bagels)