Two years ago, after 18-year-old Salvador Ramos walked into Robb Elementary School with his brand new AR-15 and killed 19 students and two teachers, surveillance video was made available to the public. The Austin American-Statesman published the footage on its website, showing the ease with which the gunman entered the school and shot his way into a classroom. Showing the delay by local police to stop him. Showing a child walk out of a restroom, see a man with a gun and run back into the restroom. Showing the nightmare that followed. The newspaper’s editors attached a disclaimer to the...