As Scott Keneally reported in “Playing Dirty” (November), nearly 1.5 million people participated in an obstacle race in 2012, and the sport’s popularity has inspired some pretty cutthroat business tactics among its Big Three: Tough Mudder, Spartan Race, and Warrior Dash. “I’m not bothered by the competitive spirit that would naturally be associated with the promotion of these events,” wrote Douglas Young, of Portales, New Mexico. “But I am troubled by the juvenile behavior reflected in that promotion. The shenanigans cited in Keneally’s article took me back to junior high.” Karen Latchford, from Palo Alto, California, wrote, “It was an in-depth, very well written article about some people I found pretty repulsive.” On Twitter, PatsHoppedUp wrote, “And here I thought people who humblebragged about obstacle races were the worst. Turns…