Not to excuse a bunch of racists, but this sounds like they were just talking about it to one another probably at some honky tonk.
Moonbat time.
More likely someone in the ATF chain of command PRESUMED that Obama was in danger, and pushed for that angle.
Or perhaps one of these 'skinheads' happened to live within five miles of an Obama yard sign.... and that was evidence enough for some aggressive law enforcement official.