As the local Male Human Paladin, I would like to clear up and explain that not only was Theramore a Legitimate Military Target, but its destruction was actually a brilliant strategy by Garrosh, and executed in a way that shows political cunning, and the desire to wage a war to kill as few civilians as possible, while still winning.
At any time, Garrosh could have sent the Goblin Zeppelin with the Mana-Bomb over Theramore, it would have arrived with no warning and with nobody being able to stop it before it dropped its payload.
Instead, Garrosh made overt moves towards Theramore, knowing that the close relationship forged during Thrall’s leadership between Theramore and several members of his own Leaders would divide their loyalties, and result in the attack being leaked to the Alliance.
This gave the Alliance plenty of time to evacuate the innocent, and brought political pressure to reinforce the City not only as a major logistical base on Kalimdor, but a place where a stand could be made. Elite troops and high ranking leadership would be dispatched to defend the City.
Garrosh then attacked conventionally in order to draw their eyes to his main forces, leading attacks personally, and risking his own life in order to provide credence to the deception.
For that, I do respect Garrosh’s character at that time. I doubt, however, that he could understand the full destructive rammifications of the Mana-bomb when empowered with the focusing iris. He was looking for a weapon that could destory the base, and likely would not have understood the full effects of it.
It was similar to what Sylvanas attempted with Teldrassil, but the end results were the exact opposite.
Theramore wiped out the Alliance High command and many of their elite troops, and destroyed their primary Logistics base in Kalimdor. Preventing supplies from reaching Stonetalon and Ashenvale overland, and allowing the Warsong and Kor’kron to regroup and recover from being pushed out of Ashenvale by the Sentinels and establishing the infrastructure we destroyed as part of Vol’jin’s rebellion.
Teldrassil broke the Sentinels, but no other major Alliance forces and it also galvanized the remaining Alliance forces into a mentality of fighting to the Death, and unlocked the potential for retaliation and the desire for vengeance.