Who are you really, Alex? Are you the boss of that crappy place or one of their lackeys?

His style of expressing himself in English is neither Chinese nor Western. I'd have thought you, of all people, would have realised that he's from Africa. Obviously, he's happy teaching at that training centre. But Nathan wasn't, so he walked. I suspect that as a westerner, he has more employment options as a teacher of English here than Alex has.
Given the lack of good jobs for many Africans in their homelands, I can understand why many are happy teaching in China, even though as a rule they cannot obtain the better jobs in China that exist in the public sector or at international schools due to color prejudice.