Facts like that cant protect you from being belittled by elitists. They read their opinion in a guide somewhere, who are you to tell them that you have actually experienced it ingame countless time and know it's fine.
But like I said, everyone can play the game in their own style. I'm having tons of fun with moonkins and elemental shamans and so on in my dungeon runs. If other people enjoy to run the same dungeon with the same classes over and over again, that's okay, too. The trick is to avoid each other by communicating before you start the run. Otherwise threads like this one happen.
Also, tank druids in raids are awesome at the current gearing/content level, but I guess that is besides the point :P