This is how: To "blow the whistle" is an idiom meaning to expose wrongdoing, usually from a position of privileged access to the information. See: https://idio

This is how: To "blow the whistle" is an idiom meaning to expose wrongdoing, usually from a position of privileged access to the information. See: https://idioms.thefreedictionary.com/blow+the+whistle https://idioms.thefreedictionary.com/blow+the+whistle This requires that the thing being reported is in fact wrongdoing. If you expose something that is innocent and innocuous, then you are - by definition - not a whistle-blower. So when a person is called "a whistle-blower" the person using that term is expressing the opinion that the subject of the exposure is in fact 1) did occur, and 2) an act of wrongdoing.