Freedom fighter is a relativistic local term for those engaged in rebellion against an established government that is held to be oppressive and illegitimate. The terms "freedom" and "rebellion" are often controversial, as often both sides in armed conflict claim to represent the popular cause of "freedom." While outside (perhaps imperial) oppressors almost always claim to be "liberators," freedom fighters also often become oppressors in the eyes of civilians.
Though the literal meaning of the words could include anyone who fights for the cause of freedom, common use is restricted to those who are actively involved in an armed rebellion, rather than those who "fight" for freedom by peaceful means (though they may use the title metaphorically).
Historically, we find that people who are self-described "freedom fighters" tend to be called assassins, rebels, or "terrorists" by their foes. During the Cold War, the term freedom fighter was widely used by the United States and other Western Bloc countries to describe rebels in countries controlled by Communist governments or otherwise under the influence of the Soviet Union, including rebels in Hungary, the right-wing Contras in Nicaragua, and the Islamist mujahadeen in Afghanistan.
The Soviet Union used the term in the same way, to describe rebel movements in countries controlled by or under the influence of the United States and other Western Bloc countries, such as Vietnam, Nicaragua, and Colombia. These rebels often used guerrilla tactics. Some were clearly assassins. The asymmetric warfare employed on both sides made many people in the West to assume moral equivalence between the two phenomena. Perhaps the more reasoned approach to evaluating these movements would be to look at their actual goals, doctrines, and practices. It would seem inappropriate to lump together the savage, Maoist Sendero Luminoso of Peru and the socially concerned, if authoritarian, Nicaraguan Sandinistas; the same goes for the Hungarian and Czechoslovakian rebels v.s. the Afghan Mujahadeen.
The term "freedom fighter", while indicating favor of some political group, often does not reflect any actual political position of those fighting. For example, to many people around the world, the leftist Sandinistas were freedom fighters. After their revolution took Nicaragua, the CIA funded a new opposition, the Contras, who were labeled as freedom fighters by the United States government and rebels or terrorists by the Sandinistas and Soviet Union. Of all political labels, "freedom fighter" is perhaps the most blunt term for "friend" - some think that it signals an unwillingness to abandon moral support regardless of methods, an unbreakable alliance between players.
The ambiguity of the term freedom makes the use of the label freedom fighter particularly useful for propaganda purposes. It is relatively simple to show that the "enemy" has done something which violates one of the many possible meanings of the word freedom, which allows the propagandist to appear to take the moral high ground by fighting for the cause of freedom. In addition to this, propagandists commonly use virtue words like freedom, which tend to evoke positive images in the target audience in order to attach those images and feelings to his cause.
Certain media agencies, notably the BBC, and Reuters aside from attributed quotes, refuse to use the phrase "terrorist" or "freedom fighter", or even more descriptive and neutral terms such as "militant", "guerrilla" or "assassin", to avoid the political repercussions of the use of such words. The BBC did, however refer to the mainly-Catholic Provisional Irish Republican Army as terrorists, while members of mainly Protestant armed groups in Northern Ireland were usually referred to as "paramilitaries" rather than terrorists. Al Qaeda militants are usually referred to as terrorists, especially since September 11, 2001. The actions of Timothy McVeigh were also described as terrorism.