Defending one's self by telling that a previous statement was a joke. Mainly used when other people were offended by said statement.
It has nothing to do with the Army Ranger Soldier, but was highly used by a french mythomaniac using the pseudonym "eversman".
John : Dude, black people smell real bad !
Dan : Damn, you're such a racist John.
John : Hey, i was just kidding man !
Dan : Hey don't you pull some Eversman Defense on me.