I don't think so. An insurgent could theoretically use terrorism as a tactic, but a terrorist isn't necessarily an insurgent, is he? To me, terrorist means someone who employs terrorism. I don't like IEDs blowing up our troops anymore than anyone else does, but I don't consider that terrorism. I do consider it part of the insurgency, which is the resistance to the political change taking place in Iraq. Terrorism, as far as I can tell, has to do with committing acts designed to instill fear in people, by attacking civilians and civilian targets. The terms should be descriptive, not derogatory. I can decide who to despise just by being told what they did. I don't need moral guidance from the media. Just tell me what they did.
I don't see why they shouldn't be derogatory when describing the lowest form of life, and I always thought the 'insurgent' was a media euphemism for 'terrorist'.