Since I'm no longer a member of any sectarian left group, I haven't been involved in such a debate for a while, but I can see the relevance of this particular seemingly far-fetched position denying that there is a civil war going on in Iraq to the US anti-war movement, and had an email exchange about it two years ago with Rahul Mahajan of Empire Notes, who certainly doesn't see the current insurgents as a group that Americans should laud as a national liberation movement. He also argues that the situation in Iraq is now a civil war, or at least close to it, commentng that: "it’s already at somewhere not too far from the level in the Lebanese or Bosnian civil wars."
I haven't seen many articles that characterize the Iraqi resistance as a "heroic national liberation movement," though there is this one which seems to be based more in the theory of resistance than the actual on-the-ground happenings in Iraq. England's Respect party also defines the current action in Iraq as such a movement.
Loretta Napoleoni, whose book may be the most detailed look into the Iraqi insurgency, describes the resistance as follows:
Beyond the myth of Zarquawi there is a much more frightening reality made up of complex forces: independent Iraqi jihadist groups that gravitate toward Al Qaeda in Iraq, Islamo-nationalist and Baath party resistance fighters opposing coalition forces; ethnic conflict among the Sunni, Shi'ites and Kurds; fully armed and active ethnic and religious militias' and an endless stream of foreign suicide bombers. This is a scenario that may well haunt Americans for decades. It is the true nature of the insurgency.
Based on what I've read from people who take the "heroic national liberation movement" line on describing the mass killings of civilians going on in Iraq, it seems like the resistance to calling it a "civil war" has to do with what this means for whether Americans support immediate withdrawl or not, and the relationship of anti-Shi'ite violence to the relationship of the Shi'ites and the US. However, with the current situation, I don't think it's safe to say that the US is simply pro-Shi'ite anymore. Also, the assumption seems to be that if we call it a "civil war" it means we have to stay there. I don't like this particular tendency in the debate, because it seems to me to deny an apparent reality in order to justify a political position, instead of basing a strategy on what's actually happening. Second, I haven't seen anyone who's in any real contact with people in Iraq take this position, which makes me think it's ill-informed. There are plenty of people who say that the Iraqis are in a civil war - and that the civil war is being provoked by the US occupation, although it would probably not end with the occupation's departure. Patrick Cockburn, whose work I linked in the last post, and more recently, Nir Rosen on Democracy Now, and Al Jazeera are perfectly capable of taking a "troops out" now position while also describing the violence in Iraq as a civil war.
But, perhaps LS and others have more to say to explain their position?