Put yourself in their place. Imagine your country was invaded and you were a resistance fighter. You'd make sure you could either melt away into the country side or the civilian population.
What did we learn at Lexington and Concord?
Of coarse it would be nice, if all civilians would leave the area, and only insurgents were in Fallujah. Yes, I think we would be allowed to carpet bomb the town then. It would be more acceptable than bombing German towns in WWII.
The sad thing is there won't be a good clean fight, because there is no option acceptable to both sides with less civilian casualties.
Being as one side brought us into this war by causing about 3,000 civilian fatalities, it looks like a dirty fight may be the only option.