Beaten like a redheaded stepchild! Hehe
GM loses in 7 moves and get mated.

Seriously, the opening has nothing to do with the loss. The opponent didn't accept the pawn, so after move 5 white is at least equal (Stockfish even says white is better).
He lost only because of 6.f3?? which would be a ridiculous blunder even by an 1500-rated player. And even then he could have fought on by sacrificing the exchange instead of getting mated immediately.
https://www.chess.com/live/game/2391528845