What's in a name?

In this one list of the day's horror in Iraq, the US military is reported to have killed some "insurgents," some "al Qaeda operatives," some "al Qaeda militiants" and some "gunmen." I know it's cheeky of me to ask, but what's the basis, precisely, for these different labels? We know they don't wear uniforms, and I doubt they have differing dogtags or business cards. Is the distinction purely literary--a reporter tiring of using the same words throughout the article, or perhaps a worker in the bowels of the printshop who ran out of capital Q's?