Terrorism has been defined as the murder or massacre of innocent men, women and children for political ends. In that sense, 9-11 qualifies, as do the Hamas bombings of buses in Jerusalem. Nelson Mandela, another Nobel Peace Prize winner, did not get life imprisonment on Robben Island for sitting in at lunch counters, but if memory serves, for plotting terror to overthrow the regime.
Groups like the Irish Republican Army are freedom fighters who are aiming to liberate Northern Ireland from an oppressive British monarchy. And many other groups like the FARC rebels, the Zapistas, and the Maoist in India are fighting for the liberation of the people. Whereas the Taliban, Al Qaeda, and the FSA are fighting to oppress the people and to induce fear into people.
From their point of view, anyway. To King George the Boston Tea Party was certainly an act of terrorism. If Canada suddenly invaded and a drone killed my family I can pretty much guarantee I would be making IEDs or finding a way to return the favor (a motive less laudable than freedom fighting but at least as morally justifiable as the drone strike that precipitated it).
If you had a free and open democratic society that also protected minority rights and unpopular viewpoints and act of terrorism could probably not fit into a justifiable category. The problem is, when so-called acts of terrorism happen in those circumstances it is usually accompanied by mental illness and is basically just a subset of serial killing (with delusion as a chaser).
So ultimately (with the sane and semi-sane) the question comes down to: If I actually believed everything this "terrorist" believes, would I support his or her actions?
I think that they aren't freedom fighters because some of them fight to give attention to some other countries to start a war. Also if you fought for freedom, would you kill other people just for the sake of it? -This means that only *some* are freedom fighters but not all of them.
I am saying "No" because the way this question is phrased suggests that *all* terrorists would also be freedom fighters. I think in some cases it is true, maybe even true for most cases, but there are still other terrorists who are not doing it out of freedom as the motive.
As an example, the 16th Street Baptist Church bombing of 1963 was an act of racism as well as terrorism, and I don't see how this event could ever be spun as "freedom fighting". Http://en.Wikipedia.Org/wiki/16th_Street_Baptist_Church_bombing