The Washington Post—whose coverage of Watergate four decades ago angered the powers that be, toppled a president, and defined courageous journalism—has unleashed a hornet’s nest of a different sort, one unlikely to earn a Pulitzer Prize. Indeed, Washington’s newspaper of record—which was purchased in 2013 by Amazon billionaire Jeff Bezos from the storied Graham family—is uncomfortably weathering a barrage of criticism from fellow journalists and others for a front-page story published over the Thanksgiving holiday. The story, by Post technology reporter Craig Timberg and published Nov. 24, purported to reveal how “sophisticated” Russian propagandists had spread fake news through hundreds...