Jon Stewart said it was a losing battle because terror isn't even a noun. Alas, it is. But the "war on terror" still is a silly thing, at least when it comes to grammar.
One doesn't wage war "on" an enemy; one wages it "against" an enemy.
Barry Leiba pointed out exactly why this is a problem in his blog. As proof, he cites the Washington Post headline: President Defends War on July 4th.
What this means is that on July 4, Bush defended the war in Iraq. There is no war against the fourth of July (though the people who've allegedly declared war on Christmas could perhaps use a new holiday to ruin for the fragile-minded masses).
In any case, the next time I see W., I'll say, "Mr. President, I have a preposition you can't refuse..."