When defending the liberty of unsavory characters, I usually write of my native England. Not this week, alas. In the state of Texas, a 19-year-old man named Justin Carter sits in prison, ruthlessly stripped of his freedom for making an offensive joke. After a Facebook friend with whom he played video games described him as “crazy” and “messed up in the head,” Carter replied — sarcastically, one imagines — “Oh yeah, I’m real messed up in the head, I’m going to go shoot up a school full of kids and eat their still, beating hearts.” He added “lol” and “jk”...