We understand rhetoric and argument primarily through war metaphors. Test this for yourself: Try to make a positive statement about argument without relying on one. You can do it, but it’s not easy. We understand argument as a war or a battle. We marshal arguments. We defend positions. We attack assertions. We re-group. We deflect. We win and lose.
And, in fact, we can use language as a (non-metaphorical) weapon, as this article in The New York Times demonstrates.