As images of protests in Southern California have flooded television and social media in recent days, a key question has emerged: Why are so many protesters carrying Mexican flags at an American political protest? The sea of red, white and green Mexican flags at anti-deportation protests this week in Los Angeles has been seized upon by conservatives who argue that the demonstrations are inherently un-American, causing some protesters to consider leaving them at home. Photos of masked provocateurs waving Mexican flags atop burning Waymo taxis spread instantly across conservative social media this weekend. Republicans pointed to them as a prime...