No doubt it was unconsidered to probably fly in the airspace above that part of the Ukraine, but the airspace was cleared for civilian air traffic and Malaysia airlines were not the only ones flying in that air corridor.
The Police have a safety principle when discharging firearms, that I believe is relevant and similarly applicable when being in control of a guided surface to air missile system.
That principle is "Keep your finger off the trigger and outside the trigger guard until you have positively identified your target and decided to fire".
The operator should not have fired that missile until the target was positively identified. They are trained to do so and easily have the means to do so.
