Alexander Mattison and the Minnesota Vikings had boarded the flight home after a tough loss earlier this season, when the fifth-year running back found dozens of hateful and racist messages directed toward him on social media. “Under my helmet, I am a human, a father, a son,” Mattison posted on Instagram in his lament and challenge to the 60-plus users to reflect on their words and the harm they can inflict. The intensity of NFL fandom that increased with the surge of fantasy football participation around the turn of the century has spiked further in the age of online betting.