Mourners attend a vigil at All Souls Unitarian Universalist Church after a mass shooting at Club Q, in Colorado Springs, Colo. on Nov. 20, 2022.DANIEL BRENNER /The New York Times News Service In the days after a gunman killed five people at a gay nightclub in Colorado last month, much of social media lit up with the now familiar expressions of grief, mourning and disbelief. But on some online message boards and platforms, the tone was celebratory. “I love waking up to great news,” wrote one user on Gab, a platform popular with far-right groups. Other users on the site...