[Dove]

It's not tactically worthless. You don't have to dig any deeper than the wikipedia article to learn about its mission:

The ABL was designed for use against tactical ballistic missiles (TBMs). These have a shorter range and fly more slowly than ICBMs. The MDA has recently suggested the ABL might be used against ICBMs during their boost phase. This could require much longer flights to get in position, and might not be possible without flying over hostile territory. Liquid-fueled ICBMs, which have thinner skins, and remain in boost phase longer than TBMs, might be easier to destroy.

If the ABL achieves its design goals, it could destroy liquid-fueled ICBMs up to 600 km away. Tougher solid-fueled ICBM destruction range would likely be limited to 300 km, too short to be useful in many scenarios, according to a 2003 report by the American Physical Society on National Missile Defense.

Upshot being, homeland defense in general, and ICBMs in particular, are not really its mission. It's designed to counter TBMs--that is, artillery. Potentially very long range artillery, but still.

Being able to shoot down artillery from the air with a lot of speed and flexibility could be useful in any number of scenarios. Probably not homeland defense, though. Oceans and all.