America’s most daring and insightful playwright tried to warn us that we were going haywire. By making him a hate object, American theater has made us all poorer. In response to a positive review in The New York Times of the recent revival of David Mamet’s American Buffalo, one young theater maker, @harharharbour wrote, “F**k Mamet, there’s nothing he has to say worth hearing. Stop giving racist transphobic playwrights platforms. This show is shit.”This tweet epitomizes what is now an entirely mainstream, and in some circles mandatory, view of David Alan Mamet, 74, of Chicago, the great American writer of...