That's an interesting mention of gloating, Brendan. It's definitely not etiquette in chess, nor in bridge. Apparently someone was banned from the Portland Club for shaking hands with his bridge partner in congratulations after a good result on a hand.
However, gloating in the form of often extreme goal celebrations is acceptable in football. Is that because it's a team game? Yet professional tennis players often throw themselves to the ground in delight before going to the net to shake hands with the defeated opponent who has had to wait at the net.
Entirely agree that the accusation by the Russian president of FIDE is sour grapes.