There is a difference between "insurgent" and "terrorist" - of sorts:
All of the violence in Iraq is being perpetrated by "terrorists", but not all of the terrorists are "insurgents". The Term "insurgents" implies that these people are from outside of the country/context of the battle.
Terrorists can be homegrown, or insurgents from other countries.
I just wish they'd use stronger, harsher, more appropriate and descriptive pejoratives to describe these scum.
Actually, in common usage it is the insurgents who are indigenous participants in an uprising.