hen Richard Saukko galloped his chalk-white Arabian horse named Traveler around the Los Angeles Memorial Coliseum almost 56 years ago, it was supposed to be a one-time stunt. Instead, the brief performance before USC kicked off its season against Georgia Tech turned into one of college football’s iconic traditions. A succession of white horses named Traveler have followed — Traveler IX debuts this fall — trotting out of the tunnel as “Conquest” plays and the costumed Trojan warrior atop the horse waves a sword. But during a rally earlier this week to show solidarity in the aftermath of the violence...