Ah, the old freedom-fighter versus terrorist conundrum. For rationalists, this is an easy question. However, for all the collectivists and statists out there, this must seem to be an impossible riddle, seeing as they can't see a difference between *government* and the whole of *society*, nor can they separate *individuals* from their *communities*.
However, if one can get outside of the socialist thinking box, then the riddle vanishes and the truth becomes starkly obvious; just look at who the targets are.
A freedom fighter wants to live and let live, fighting against those individuals who intrude upon his (or sometimes someone else's) private lives. Freedom fighters target tyrants and their agents but do not seek to replace them with just another brand of tyranny.
By contrast, a terrorist spreads fear among a whole populace, killing indiscriminately to threaten all. Terrorists usually aren't fighting for anyone's freedom. Instead, they're usually fighting for their own chance to be tyrants, hence their disregard even for the lives of the people they may claim to be "liberating".
In the eyes of collectivists/statists, attacks on civilians are the same as attacks on the government: Each is an attack on the "nation". An attack on a busload of Israeli children is an attack against Israel. An attack against the Israeli army is an attack against Israel. To the collectivist/statist, there is no difference. The idea that school children are unlikely oppressors doesn't occur to the statist.
Similarly, the fact that an attackers' stated goal is to replace a free commercial democracy with an Islamo-fascist dictatorship never deters a collectivist from thinking that the attackers might be somebody's freedom fighters. The collectivist has already demonized individualism in favor of socialism and called it "freedom". After that, Islamo-fascism is just another cultural flavor. It's all relative.
Adding to the confusion is the fact that terrorists often use the word "freedom" in their propaganda, and some even seek to overthrow tyrannical regimes. They're not all stupid; the mantle of "freedom fighter" is good camouflage, especially when one is appealing for support from abroad.
However, we can still spot the terrorists by their methods and expose fake "freedom-fighters" by their goals. If militants focus their weapons at the weak, and especially if they aim at people they claim to be freeing, then they are terrorists. If militants seek to install an oppressive government (interfering with commerce and/or life styles), then it is possible that they might not be terrorists (in spreading fear), but they're definitely not freedom fighters either. I guess we just call them militants until we can call them corpses.