A 1953 United States Air Force report defended the operation as the justified bombing of a military and industrial target, which was a major rail transportation and communication centre, housing 110 factories and 50,000 workers in support of the German war effort.wikipedia
As @Luke has said, this is a far broader and more provacative question than is normally covered on this site, but I choose to take OP at his word and attempt a brief answer. I'm also going to endorse and respect OP's request to ignore the moral side. That isn't to say that there is no moral side, but merely that the OP requested that it be out of scope for the answer.
WWII was a total war
The Second World War can be considered the quintessential total war of modernity. The level of national mobilization of resources on all sides of the conflict, the battlespace being contested, the scale of the armies, navies, and air forces raised through conscription, the active targeting of civilians (and civilian property), the general disregard for collateral damage, and the unrestricted aims of the belligerents marked total war on an unprecedented and unsurpassed, multicontinental scale. wikipedia: Total War emphasis added
According to the theory, victory depended on the ability of the nations involved to muster an unprecedented level of industrial committment, and to deliver that to the front. Defeating the adversary's army merely prolonged the conflict; victory was only possible by degrading the adversary's ability to produce and deliver military supplies.
Dresden was a critical junction of communications and industrial production. Destroying Dresden halted the production of military supplies and delivery to the battlefield.