Morally, and in terms of international law, recourse to arms is sanctioned. The right of a people suffering from colonial oppression to take up arms in its struggle for independence is established by virtue of experience, morality and law. The concept of terrorism, on the other hand, is farcical, from a moral and legal point of view. Arbitrarily grounded in the foreign policy interests of the US, to pay any attention to it would be absurd. Law, as any secondary school student knows, is supposed to be general and abstract.
Morality is supposed to be moral.
Then there is the charged, symbolic significance of armed struggle in the history of Palestinian resistance. The Klashnikov became a symbol of Palestinian struggle and nationhood. We might look also at the conduct of armed struggle in the current Intifada. He's got a gun, he will fire it. Ultimately, however, it is a question of strategy not justification.