Military Target = Soldier
Civilian Target = Terrorist
To make sure there is no mistake, military targets include the enemy military (obviously), the enemy military command structure, the enemy military production facilities, and things that are generally painted green (army) and grey (navy).
Civilian targets are targets that are not military. Some of many examples are police officers, schoolchildren, pregnant women, firemen and puppies. The enemy nation's financial district would fall under this catagory. That is why blowing up the WTC was a terrorist act, just as the IRA attack on the London financial district was a terrorist act.
Your diatribe goes to motivation. Of course the IRA is motivated (mostly by Marxist nonsense, BTW). The distinction between soldier and terrorist is all about methods. The IRA should just own up to the fact that they are terrorists and that they find terrorism acceptable in light of their grievances and circumstances. They can make persuasive arguments that they are opposed by terrorists, and thus have no choice. But they should be prepared to call themselves what they are, terrorists. Then the world can decide what they think of them.
Fortunately, the world has very little patience for terrorists just now. Long may it be so.