"Terrorists are not a country."
That will not be the general view a year from now. Iran must be funding a lot of the Iraq insurgency. N. Korea is a terrorist state. We'll have no problem using nuclear bunker busters when the time comes. There are comparatively low yield with no mushroom cloud, so there won't be as much outcry. And they will be used after the stage is set by some massive terrorist strike (bigger than 9-11), so hearts will have hardened.
And after a dirty-bomb explosion there is still the problem of which country to attack. We can't and shouldn't level them all.