The Justice Department’s chief peacekeeper is on his way to embattled Ferguson, Mo. Usually, Grande H. Lum flies under the radar. As head of the department’s Community Relations Service, the Harvard Law School graduate is an experienced mediator, more diplomat than prosecutor. The agency he heads was established under the 1964 Civil Rights Act, with the stated mission to aid communities “in resolving disputes, disagreements, or difficulties relating to discriminatory practices based on race, color, or national origin which impair the rights of persons in such communities.” “These officials will continue to convene stakeholders whose cooperation is critical to keeping...