No good deed goes unpunished. The truth of that adage was confirmed in spades last week when a Montana couple, Jason and Tara Shane, described as Good Samaritans for helping a stranded young, Mexican motorist were shot and killed for their effort. Their daughter, Jorah Shane, 26, was wounded. Jesus Deniz Mendoza, 18, a Mexican national who entered the United States legally two years ago, shot the Shanes when they stopped to assist with a broken-down car. Shortly after the shooting, U.S. Immigration and Customs Enforcement indicated that Mendoza had legally entered the country from Mexico through the San Ysidro...