Mark Twain? Abbie Hoffman? Roy F. Nichols? George McKinnon? Aardvark Magazine? Graffito? Dear Quote Investigator: The following has often been ascribed to the famous humorist Mark Twain and the 1960s-era political activist Abbie Hoffman: Sacred cows make the tastiest hamburger. Apologies for offensiveness. Would you please explore the provenance of this expression? Quote Investigator: QI …