Logical fallacy/No true Scotsman

The "No true Scotsman" argument is an argument of the form:

Argument: "No Scotsman puts sugar on his porridge."
Reply: "But my friend Angus likes sugar with his porridge."
Rebuttal: "Ah yes, but no true Scotsman puts sugar on his porridge."

Atrocities of religions are often discussed away using this fallacy.

/talk