At the first use of the word irony, they come swooping in to demonstrate their intellectual superiority, without bothering to check whether the usage was correct or not.
"That is not what irony is!!" said the Irony Nazi.
Someone who scans every use of the word irony, and if it doesn't rigidly adhere to Ed Byrne's definition of situational irony, he proceeds to attack, often reciting Byrne's stand up act. See also irony police.
Some guy: "Poor Chuck Norris's fans only appreciate him ironically nowadays..."
Irony Nazi: "Hey! That's not ironic, that's just unfortunate!!"
Some guy: "Wha?"
Irony Nazi: "Irony is when there's a gap between what happens and what was expected to happen!"
Some guy:"No, that's verbal irony..."
Irony Nazi: "Silence! Ed Byrne told me that when people don't use 'irony' the right way, it's just unfortunate and not ironic! Heil Ed Byrne