Maybe not an A+ in Ethics class.
I have a friend who held down a 4.0 GPA this past term, but I have it on good authority that he wildly plagiarized some, if not all, of his final papers. I am tempted to anonymously tip-off the relevant professors. Then again, he is a friend, even if not a close one. Would it be unethical to put that note in the mail and still act like friends?
Suppose there’s a local coffee roaster whose website makes elaborate claims of rare, single-origin beans and innovative roasting techniques. You don’t love their coffee, you don’t hate it. Following a chance encounter at a brewery tasting event, a disgruntled ex-employee tells you that the roastery just throws Cafe Bustelo in an oven with vanilla beans and bay leaves to pooch the flavor profile. Your tip to the local paper’s coffee columnist results in the roaster’s widespread discrediting. The question isn’t, “Should you feel bad about drinking their coffee?” it’s, “Do you want to be getting coffee there at all?” Which is much easier, considering the fact that you’ve already made your mind up about exposing the cheating.