It was far more than one incident... more like that sort of thing was normal behaviour, and the best you could hope for in a random group was one which was silent and nothing went wrong. Everything was on a knife edge, hoping that things went smoothly and was over with quickly before someone exploded.
The whole idea of
"It can't happen here" fails to take into account that WoW was once a far more pleasant place to be, raising the question of what went wrong in the first place? I wouldn't place the blame solely on the misuse of parsing tools, but again, they do seem to be the longest-lasting means of propagating toxicity in that game.
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That being said, I've tracked down the "official response" on parsers; it was put in Live Letter LVII, to summary of which can be found here:
https://forum.square-enix.com/ffxiv/threads/414393
And to pull a quick quote from the first post there:
Calling people out for low DPS is considered harassment, full stop.
Parser or not, they don't want that happen under ANY circumstances.