I despise Islamic terrorists asshole. I support people that resist occupation and oppression.
You are making an error in determining whether an act is one of terror or one of "resistance" by using just cause as a measure. The problem with just cause is that it is subjective. Everyone who commits an act of violence believes they are acting for a just cause. The only difference is that their just cause may not seem so just to you, so you call it terrorism instead.
The Israeli Arab conflict is a perfect example of that. The Arab Palestinians are fighting against occupation and oppression, right? A just cause if ever there was one.
The kicker is that the Jewish people are fighting for the exact same just cause -- against occupation of their historical, ancestral, and religious territory of origin and the thousands-year-old oppression of their people. A just cause if ever there was one.
Now, I know you don't agree with my assessment of the equivalency of these two just causes. But, it doesn't matter. As I said, its subjective. People act based upon the causes they perceive as just. If that were our only measure, then there is no such thing as terrorism as differentiated from resistance. Every terrorist is resisting something, according to his own perception.
I would suggest we need another measure to distinguish between terrorism and resistance. I would suggest it depends on achievable goals and whether or not those goals can be achieved through other means. It depends on whether chosen targets minimally attempt an objective towards achieving those goals.
For example, attacking Israeli police forces at checkpoints, could reasonably be seen as an act of resistance in that, at least nominally, it is a military objective to disrupt the military and police forces in order to achieve the stated goal of "end oppression and occupation."
Stabbing or fire bombing children in their homes, running over civilians in trucks, attacking civilians with hammers has no objective other than to create fear. Thus, terrorism and not resistance.
You can apply the same measure to London. If the intent is to topple the British government in order to achieve an Islamic Caliphate and you do it by blowing up Parliament, one could argue that there was a military objective to that action.
Setting off a bomb at a concert attended mostly by children is terrorism.
