Carmack says that he wants objective arguments, not emotional ones, and all this blog presents is yet another emotional argument. All that stuff about the community 'roaring' is avoidable hyperbole.
All these concerns are valid concerns and not just many if's and if they are not addressed now, in the future will be (already is actually but anyway) too late to do anything.
Say you are developing a game (which is the case here) or a 3D application based on OR. Now you might be ready for a bunch of AppStore-like rules to kick-in. This could make your product obsolete in no-time.
I don't think that the concerns of the community are irrational, quite the opposite... The community is concerned out of experience and knowledge of Facebook's prior policies.