If gun control worked, the president’s hometown would be safe. Instead, gangs of fatherless youths daily kill other fatherless youths. How about an executive order endorsing marriage and intact families? We do not know how history might have been different had the parents of Newtown shooter Adam Lanza not divorced in 2009, leaving the troubled young man with his mother in a single-parent home. But if there’s a thread that links the carnage at Sandy Hook with the 500-plus murders in Chicago in 2012, it’s not just the use of guns to kill. It’s also the absence of an intact...