Here is the thing. GSP didn't retire. He said he is going away for a little bit. Rogan even asked him if he was retiring and GSP I believe so no, Or at least did not answer the question.
So, with that being said I can see Dana's reaction. The whole thing was very strange and something just isn't right. Who knows what it is, but I bet had Dana not said what he said most people would have the same kind of reaction.