Fair enough. So by that measure, no-one outside Argentina can be said to be dancing Argentine Tango, ever, correct?
Dave was asking a rhetorical question (i.e. he's not actually saying he believes or advocates that position, but rather trying to make a point).Why? There is no reason for this deduction: nothing prevents you from dancing in Australia or in China the same thing that is danced in Argentina socially.
And nothing prevents you from dancing a different thing: in this case you may want to call it with a another name, or not. Everything depends on your definition of AT. Calling it Australian Tango or Chineese Tango could be an option.