A lot of people are saying that the reason Rassie clapped back is because Rennie 'got in his head'. Some even go as far as saying that the Boks are rattled because their tactics were exposed.
I think Rassie articulated very well that he didn't mind the banter, but he did mind how it affected the game.
For me the problem is that the first thing the ref said to the Bomb squad (Literally before their first scrum even set) is 'don't walk around', which is what Rennie has been saying they do the whole week.
Imagine if you bring on a replacement kicker and before his first kick the ref says 'Remember you only have a minute to kick.' because the other team complained the kickers take to long.
The banter also seemed to affect scrum resets as more often than not, when if collapsed the scrum was reset rather than a penalty.
Seems to be a lot of people who pearl clutch at Rassie's language (They should wat Chasing the sun to see how colorful language can get in the changing rooms XD) but his frustration wasn't at Rennie saying stuff, but at how that stuff was affecting his players and the game.
I think most see Rassie as a 'bok vir sports' but he does not like it when shenanigans off the field affects his players.