One other point. 9-11 is universally held to be a terrorist attack. By arguing "We shouldn't use the word terrorist because we dispute the very conception of terrorism" we are engaging in political advocacy.
Wikipedia should try to properly reflect the world more than it should try to shape it.
We already have an excellent discussion of the fuzziness of "terrorism" in that article. That's the place for such a discussion, not in the Sep. 11 namespace.