How does it sound like gloating? This is strictly a chess.com thing. On Heroes multiplayer, Age of Empires, Age of Mythology etc.) Both players always say GG and nobody thinks it's gloatig or disrespectful. I was surprised to find that this wasn't the case on chess.com, the first 2 player game I had ever seen where it is not common practice for both players to say gg.
First of all, why do you think a loser is "stinging from the defeat"? Chess is just a game, losing a chess game isn't like getting passed over for a promotion. If I lose a chess game, it means nothing. If I start a chess game and then get interrupted by something out of my control, I'll just offer a draw and then resign if it is turned down. Who cares? Just more games for me to analyse and learn from. I don't imagine my opponents curled up in a ball sobbing if I beat them, I imagine them either going "hey that guy played pretty well" or "dang I wish I had done something different on move x". There's nothing emotional about this, and your logic assumes that people take losses personally.
By the way, nice use of magnanimousness. I had to look it up, I'd never heard that word before.
But I don't know what's wrong with it - if a game was good, one should write 'gg' no matter the result.
Some people, no matter what, only want to find the worst in others.
Why are you trying to find the worst in the implied straw man of your point?