Terrorism -- defined as deliberate attempts to kill and injure civilians -- is just a tactic.
It is a tactic used by all serious people who have, or wish to acquire, power, when they feel that it is in their overall interests to do so.
The human species is slowly and fitfully moving toward acknowledging a set of universal ethics in which terrorism -- deliberate attempts to kill and injure civilians -- would be seen as wrong.
We in the West are a bit ahead of others in this. But this change is glacial. At the moment, most people, save for a few eccentrics, are very happy to see the women and little children of their enemies burned alive, or shot, or blown into bloody fragments. This is just the nature of the human animal.
Is the current movement of radical Islamists motivated by concern over "social justice"? Where they have had power -- such as in Afghanistan under the Taliban, or in those areas of Iraq which were controlled until recently by Al Queda -- can we say that they implemented "social justice"?
That seems quite a stretch to me. People who think this is so seem to be assimilating reactionary Islamic fundamentalism to communism. But these two movements have little in common.
What is true is that the ultimate driver for Islamic fundamentalism is the backwardness and stagnation of the Islamic world. The real -- as opposed to ostensible -- motivation for invading Iraq was to address this problem: the neo-con theorists of this invasion believed that Iraq -- a relatively advanced, relatively secular, and potentially oil-wealthy country -- could be kick-started into liberal democracy, thus triggering a reverse "domino effect" on the rest of the Middle East.
Although they were tragically wrong, it is not beyond possibility that, in its own way, slowly and with setbacks, and wading through blood to get there, Iraq may yet embark on a "normal" course of development, and become an Arabic Turkey. (That is, Muslim, but undergoing normal capitalist development, with the slow growth of the rule of law and the education of its population towards de facto secular norms.) However, we are talking decades here.
Thus I hope that President Obama does not precipitately withdraw our forces from Iraq. That would only be justified if he believed that there was either no chance at all of a reasonable democratic development, or that there was one, but that our presence was irrelevant to it, or a positive hindrance.
Those who believe the latter, must then ask themselves: if Iraq, why not Afghanistan?