It's traditional in football for the coaches to shake hands after a game.
College basketball teams often shake hands with the opposing coaches and players.
You are right, of course. The team that lost the Series often looks on for a few minutes, thinking, forlorn, about what might have been. No mood for cordiality.
Where the rabbi is wrong is this: the winning team are fools if they don’t say “we just beat a great and mighty team of stellar players and feel blessed to have gotten past them”. And so I heard many Braves players say, to that effect.
I don’t like team sports, but an exciting baseball game is the exception. I was rooting for the Braves. Since I don’t watch often, I had no clue what the protocol is. Thanks for clarification.