Earlier quoted context omitted.
No, the error is Hank's, for not reading that sentence in context. John is addressing an existential claim made by Jason Snell: Snell’s argument is that Apple should do this to nip the argument that the iPhone is too closed. But if Apple did exactly what Snell argues, critics would still harp on the closed App Store.
I'm not sure how that context changes the sentence. If you're saying Gruber is referring to those critics in particular (rather than all critics, or critics in general), he should have started his sentence with "These iPhone critics..." Or, to add context to my test sentences: "John Smith weighs in at an astounding 350 pounds, but that's not hard to understand. Americans rarely get any exercise." The second sentence…
The context makes it obvious which sentences are part of the author's thesis, and which are snark. Quoting the snark in isolation tells you only that Gruber is capable of sarcasm.
Edit: what's most interesting to me here is that Hank doesn't seem at all interested in Gruber's thesis, let alone in attacking it. He just seems interested in attacking Gruber.