The magazine Christianity Today—which bore the imprimatur of its founder, Billy Graham—once arguably represented the broad middle of “American evangelicalism.” But a recent editorial calling for President Trump’s removal through impeachment confirmed the magazine’s creep toward that Slough of Despond populated by liberal elites and Joe Biden.

The article cleared its throat—and conscience—by declaring “unambiguous” the “facts” of the president’s guilt. Having thus defenestrated objectivity, the editorial cited his behavior...