Very much reminds me of a Kids in the Hall skit from ages ago. Two guys are at a party, one says "hello", the other says -- in perfect English -- "Sorry I don't understand you, I don't speak English. please don't beat me up." The first guy assumes it's a joke and plays along until he gets annoyed at the perfect accent and responses ("no really, I don't understand what you're saying, nor what I'm saying, I've just practiced this conversation a lot. please don't beat me up.")
Eventually the first guy tires of being mocked by this guy claiming not to speak English and beats the guy up.
Totally hilarious example of what you experienced taken to an extreme.