I'm really not trying to pick a fight, but isn't this just the common use of rhetoric and re-definition that one would find in commentary?

I think your example is a great one. The conservative would then proceed to argue that his definition of "progressive taxation" is adequate for the discussion at hand.

I'm probably just making a big deal out of nothing. I'm just flummoxed at why his own technical field's definition has anything to do with communication directed at a non-technical audience.

Perhaps he used it like that to get the response you gave? That would make sense.