Our experiences are different. In most raiding guilds I've been part of, we might whined about afkers on trash, but we really tolerated it. And especially as I told in another post, that slacker is carrying the guild by being consistently first on mechanics and damage or healing on bosses, good luck threatening to kick him. Or if the slacker is someones brother, or best friend or girlfriend.
On the image posted there is a warlock with less damage than the poster, and there are several other dps who aren't playing at their top potential. And if we go through all of the logs, which i can't be arsed, my guess would be that this whole debate is an overeaction. Slacking is human nature, slacking on trash is common to make it such a big problem.