Former President Donald Trump’s campaign fired back at the Foo Fighters, who last week said the campaign didn’t have the band’s permission to use its 1990s anthem “My hero.” Trump’s campaign on Friday afternoon played the song as he welcomed Robert F. Kennedy to the stage at his Glendale, Arizona, rally. Kennedy’s walk-out to the song — with fireworks igniting behind him and Trump — caught the attention of the band, which delivered a stern response. “Foo Fighters were not asked permission, and if they were, they would not have granted it,” a spokesperson told Billboard on Friday night. The per…