Just What Do You Mean By "Christian?"

Because I lived in Michigan for twelve years, I've watched with some interest as events unfolded following the arrest of twelve members of the Hutaree "Christian Militia" group last month.  The arrests broke up their apparent plan to kill local law enforcement officers.  There are lots of things to ponder with this, but the one that I keep coming back to is their designation as a "Christian" Militia group.  Christian?  How so?