Planning stages for a dirty bomb is not cause for a warning or evacuation of Washington DC, althought closing the city down might save us some money.
Why not? Most of the warnings now are unconfirmed non-specific (UFO)reports anyway. So why is this different? Who said anything about closing down a city. Especially in DC, nearly impossible. Besides that threat of a RDD is not really mass death.
Yes there are times when issuing a warning is mindless, depending on the way its done.