Last week, 88-year-old James W. von Brunn walked into the U.S. Holocaust Memorial Museum in Washington and opened fire with a .22-caliber rifle, killing security officer Stephen T. Johns. This appears to be the third politically motivated murder within 30 days. Do you remember 23-year old Pvt. William A. Long being shot and killed outside an Arkansas recruiting office, allegedly by an extremist upset about the U.S. military presence in Iraq and Afghanistan? Then there was the murder of Dr. George Tiller while he was serving as an usher during a Sunday church service in Kansas. His alleged killer is...