According to this post by George Soros on Huffpo, four factors ensure that the alleged “war on terror” cannot be won.

Calling the problem a “war”

1. Invites killing innocent victims;
2. It prevents the U.S. from differentiating among organizations that should be treated differently. 
3. It overemphasizes the need for military action and
4. It invites us to paint ourselves as entirely blameless for everything we do.

In short, pre-defining our sharp political differences “wars” means that we will treat them as wars.  In wars, we dehumanize the other side, call our opponents crazy and we drop bombs on them, it’s just too bad that we sometimes need to separate their innocent children from some of their limbs.  Treating all conflicts as “wars” causes us to lose sight of alternate approaches for resolution.

I agree with Mr. Soros, that the “war on terror” is a bad metaphor.  Terror is a tactic, not something identifiable on which we can drop bombs–though that hasn’t stopped us from trying.  Since terror will always exist (people who are angry enough at the U.S. to do violent things will always exist), the “war on terror” will never end, by definition.  Using this label of “war” justifies massive domestic deprivations and a ever-lasting gorging of the military-industrial complex.  Using the label of “war,” in conjunction with “terror” is a narrow, useless and bloody frame of meaning.

It can often be useful to posit a thing for a process; in Metaphors We Live By, Lakoff and Johnson, refer to metaphors like this as ontological metaphors.  “Inflation” is an example of such an ontological metaphor. But ontological metaphors are not necessarily truths in the sense that it is true that 2+2 =4 or that it is true that I have a stomach.  All metaphors are models.  All models emphasize certain aspects of reality to the neglect of others. 

The “war on terror” metaphor overemphasizes and makes salient exactly those things that Soros sets forth in his well-written post.