Well knowing someone is a moron is not the same as stating it. I was illustrating my point And I used the word as a generalization for stupid, I didn't know it was synonymous with "retard".

But, the same thing can happen because of the language barrier. Imagine a foreign exchange student coming to the USA (for example) and someone telling him he looks like a fruitcake. He might take it as a positive thing. It was an intended insult for all to hear, meant to ridicule that person. If someone else who knows what that meant explains it to him, he has every right to be offended.