I just finished teaching on Sosa’s safety-based defense of Mooreanism. Here’s a counterexample to safety I made up for my class. (An informal survey, on a 7-point Likert-scale, suggests the intuition enjoys strong support.)
BANNED ART EXHIBIT: The Art Institute is hosting an exhibit on banned art. There is one particular very valuable piece that incredibly irks you—it offends every one of your religious and moral instincts. You dash off an angry letter to the Institute threatening to destroy this piece. Your letter is so convincing that the officials would secret away that piece of art and replace it with a believable fake. You send the letter but it gets lost in the mail. Completely unaware of the intrigue, Sally goes to the Institute and sees the controversial piece of art. Sally knows that this piece is at the Institute even though her belief is unsafe; in close worlds where the letter isn’t lost in the mail she forms the same belief (through the same method) even though it’s false.