Debates often lead to discussion of extremes or well known situations where an answer is more easily figured out, and then that is applied to the topic at hand. In this case, George Washington was in a similar situation, taxed and squeezed to the point of rebellion, and most people know his situation.
But anyway, if simply making the enemy fear for their life makes you a terrorist, than any soldier in any conflict anywhere can reasonably be called a terrorist. The term implies that you are intentionally trying to cause civilians to be scared for their safety.
George Washington had no such intentions, his problem was with the English parliament, rather than everyone in England.
Judging by my limited knowledge of the games storyline, I think this is similar to the resistance. They are simply fed up with the policy that the leaders of the founders have set up, with the refugees getting less rations. The security are in the way, and must be fought, but i don't expect you to have any missions where you are shooting civilians for the sake of terrorizing other civilians.
Terrorism is: a person who terrorizes or frightens others (taken from dictionary.com). It doesn't matter whether or not it is a civilian or an enemy combatant. Therefore, one could make the claim that a combat personnel is considered a terrorist by their enemy. The Resistance hopes to bring about change by causing the founders to fear for their lives, which would earn the Resistance equal food and water.
On the other side of the coin, Security employs terrorism right back at the Resistance. They hope to make the Resistance fear for the lives of themselves or their families. If the Resistance is terrorized enough, they will lay down arms and accept their second class citizenship.
I'm not arguing one side over another; again, someone's hero is another's villian. I'm just arguing the philosophy of terrorism itself.
I've had fun debating with you, good sir.