President Joe Biden’s prime-time speech Thursday night, which featured a blood-red backdrop and a grim warning about the endangered “soul of America,” drew fierce reactions online, with critics branding the content divisive and the theatrics just plain weird. Biden, who framed the upcoming midterm elections as a fight between good and evil, stood flanked by U.S. Marines outside Philadelphia’s Independence Hall. Unusual red lighting cast a fiery glow on the brick building as Biden railed against supporters of former President Trump, who he said have taken over the Republican Party. “MAGA Republicans have made their choice,” Biden declared. “They embrace...