GT: Interesting that he really didn't know what diversity even meant.
Actually, Terry used the term in a slightly unconventional way initially and then changed his meaning several times during the discussion. Although every way the Terry used the term is within the range of meanings for the word, I think most people would have been uncertain how to respond.
From reading the dialogue it becomes clear that Terry really was trying to get the elder to admit that no dissent, disagreement or questioning is allowed. The WTBTS is a totalitarian group insisting on complete, unquestioning obedience to the dictates of the leaders.