After a Minnesota police officer fatally shot a black man on Wednesday, gun control advocates weren’t the only ones criticizing the National Rifle Association. Some of the blowback was coming from within the organization. The NRA is facing internal division as its members argue that the group did not do enough to defend gun owners’ rights by speaking out on behalf of Philando Castile of Falcon Heights, Minn., who was shot to death during a traffic stop. Castile had a valid permit to carry a gun. He also reportedly informed the officer who shot him that he was armed in...