The celebrating began before the coroner could collect the bodies of Alyn Beck and Igor Soldo, the Las Vegas patrol officers ambushed and executed while eating at a pizzeria last month. “The good news is, there are two less police in the world,” read an entry on the Facebook page for CopBlock.org. The post was visible for less than a day, but it attracted at least 6,300 likes and comments by the time the page’s administrators removed it. Jerad Miller — who along with his wife, Amanda, gunned down the Vegas police officers before dying during a shootout with police...