Via the BB Submitterator, reader muis says,
A 17-year-old kid (or "woman", as the press prefers to call it) is lassoed and dragged by a horseman after she and other animal rights activists entered a corral to protest against the rodeo. According to the news article linked here, the Chilean Rodeo Federation's director "regretted what happened, but at the same time justified the attitude of the riders".
Her name is Constance. From the YouTube description: the incident occurred on September 19, during the "Patriotic Celebration Festival" at the National Stadium. The video shows three young people entering the corral to peacefully protest animal abuse by the rodeo; then we see riders on horseback and rodeo men on foot lassoing one female protester later identified as a 17-year-old child.
Any Boing Boing readers know whether a specific animal rights organization was behind the protest?