This one is tough to decipher. The NME
review of the album said the song was about a psychopath and a killing spree, which tied in with the "Stevie, where you going with that gun? Who you wanna shoot down? Who you trying to kill?" lyrics.
As Dina at The Kasabian Wiki
points out, this is not the case. "It's about believing in yourself and standing up for what you believe in," she explained. "It seems like the song is just as misunderstood as the character Stevie, because people make assumptions after hearing only the first line and nothing else."