I would argue that many of the most successful military campaigns have involved total warfare, which includes targeting civilian populations. The strategic argument is that it demoralizes your opponent, disrupts his economic system and supply of materiel, and damages his political power and control.
The trend towards less aggressive use of total warfare seems to be mostly a byproduct of media exposure of the military theater to non-combatants, resulting in negative public opinion and diplomatic pressure.
The US, for example, could have put down the Iraqi insurgency after the invasion in a manner patterned after Fallujah -- expel civilians, ring the city, and level it going after insurgents. We most likely would have killed enough insurgents and cowed the population to end the insurgency. However, public opinion and diplomacy would have made widespread destruction quickly unpopular, especially with a domestic audience already somewhat divided by the war.
It might even be argued that *not* pursuing total warfare resulted in greater suffering by stringing out the conflict over a couple of decades and leaving the theater badly damaged regardless. It also results in high costs for the aggressors, as they expend lives and materiel without really accomplishing their goals.