Your contrived example falls flat because JSON is flat out better for most use-cases and anyone having a discussion about it will probably fit into those use-cases.
People don't discuss solutions in a vacuum. Ideally they'd think about what the potential fallbacks of using XML alternatives are before jumping into a new tech. Which they will, unless they're really really new
JSON is worse than XML if your use case requires namespaces.
Tangentially, this is one of the reasons that I am a fan of EDN[1] over JSON.