I've seen the paper, but it assumes the point in question in the definition of partially rational agents in the very first paragraph:

If these agents agree that their estimates are consistent with certain easy-to-compute consistency constraints, then... [conclusion follows].

But peoples' estimates generally aren't consistent with his constraints, so even for someone who is sufficiently rational, it doesn't make any sense whatsoever to assume that everyone else is.

This doesn't mean Robin's paper is wrong. It just means that faced with a topic where we would "agree to disagree", you can either update your belief about the topic, or update your belief about whether both of us are rational enough for the proof to apply.