So somewhere between 3,000 and 25,000 it becomes a massacre? Sherman also didn't have bombers and his opponent hadn't declared total war on him first....

I don't know about the 3000, but I'll accept it for the sake of the argument. I'd say that if Sherman rounded up 3000 and executed them in one or a few days, sure, that's a massacre. Even 300. But while scattered killings are bad, I don't think they qualify as a massacre.

I shouldn't have brought it up it wasn't germane.

No, it's a perfectly fair question. Only people who proudly wear hypocrisy on their sleeves will whine about 'whataboutism' when called out about it - they don't even know what it means.

Destroying the enemies capability to continue warfare is the highest ideal. Do I think the Allies first priority was the reduction of civilian casualties, no obviously not. But their main purpose wasn't the destruction of human lives.

That is a very broad formulation, which may include almost any action. Perhaps massacring an entire city would destroy the enemy's morale (as you said) and thus reduce the capability to continue warfare. Regardless, I don't know enough to the specifics to either confirm or contradict. Only that the raid on Dresden, even when viewed with the most rose-tinted glasses, is grossly disproportionate to what they were supposed to get from it.