IEDs are no more or less cowardly than us dropping smart bombs on them - both weapons strike without warning.
How many non-combatant Afghans have been killed by IEDs? Not all are command-wire detonated.
I know that non-combatants have been killed by ISAF weapons, but huge efforts are made by the aircrew and JTACs to ensure no civilians are in the kill-zone of the weapon.