It’s presented as a slideshow, which is an insult in itself, but no matter: the British radio station Classic FM presents 21 of the best insults in classical music. I’ll just quote one, from Louis Schneider on Debussy’s La mer:
“The audience expected the ocean. Something big, something colossal. But they were served instead with some agitated water in a saucer.”
I mention this one in particular because La mer may have been a target more than once. Meredith Willson (The Music Man) once told a story about Erik Satie, who had accompanied Debussy to a performance: after the “Dawn to noon on the sea” movement, Satie is supposed to have said sort of loudly, “I just love that part at about a quarter to twelve.” Debussy promptly unleashed a few French translations of Anglo-Saxon, concluding with accusing Satie of being an inept and unlikable composer. I’m not so sure about this, since Satie is supposed to have taken his umbrage to his desk and pounded out Trois morceaux en forme de poire; but said morceaux were completed in 1903, and La mer wasn’t finished until 1905. Maybe an early version getting an airing?