Representative Alexandria Ocasio-Cortez on Tuesday helped host an online event aimed at encouraging young people to vote that was organized by an activist who said last year that “America deserved 9/11.” The New York Democrat congresswoman, 31, spoke at the beginning of the virtual event, which was streamed on Twitch, and announced an “amazing lineup” of gamers to play “Among Us,” a newly popular video game. Hasan Piker, a vlogger who last year came under fire for saying “America deserved 9/11,” organized the event, which featured popular Twitch streamers along with Ocasio-Cortez and fellow congresswoman Ilhan Omar, who herself has...