In global political discussions, one must view all possible viewpoints. It is sometimes stated that one man's terrorist is another man's freedom fighter. Nations or radical or reactionary factions within nations may not necessarily have the funding to fight someone or something that they feel must be fought.
However, there is a difference between guerilla tactics and the methods employed by terrorists. Whereas the former employ means that are along the border of acceptable military conduct (and may go over), terrorists tend to slaughter innocent civilians, sometimes in the thousands. The difference in scale cannot be overlooked.