Federal registration is the T.S.A. PreCheck of intellectual-property law: Not everyone has to get it, but if you do a lot of business, you probably should. The problem is that in the Slants’ case, the trademark office has come to look a bit like the popular image of the T.S.A.: a bureaucracy of bored enforcers just trying to churn through the queue and get through the day. Except that every now and then, something complicated comes down the screening belt, or someone gets a little overzealous about the job, and everyone winds up looking bad.