I would say that portraying Ulysses S Grant as a 'butcher' has passed largely from academia. I've only read the thoughts of John Keegan and Sir Michael Howard on the matter, but they both agree on some fundamental principles - Grant's use of his troops was less butchery and more an acceptance of the underlying strategic situation: everything the North took from the South was, man for man and pound for pound, more valuable than vice versa. Secondly, Grant had an incredible ability to utilise what was a very different army to that which he had served with in the Mexican-American War.

One thing that has occasionally earned him the title of 'butcher' is based off that last point - as Abraham Lincoln put it 'he fights'. The citizen-army brought about with the Civil War was not one that could be rigorously disciplined and expected to withstand and remain integral through retreat and withdrawal. Instead, Grant appreciated that his staff, and thereby his soldiers, had to be pushing forward; Keegan states that the casualties suffered by the Union soldiers did far less against moral at the Battle of Shiloh than the fact they were being pushed back against the river. It was Grant's decision to counter attack that truly brought a surge in morale - alongside Grant's confidence that Johnston had overextended his troops.

Grant fought, because he understood that his army required it. Grant never, ever fought in such a way that overextended his army and strained his supply lines to breaking point. He wasn't a butcher, in the same way Sherman wasn't a murderous despoiler. He was a man who understood that ending the war as quickly as possible helped the United States, North and South. Pushing forward, despite casualties, might have been worthy of the title 'butcher' had he placed his troops in a position from which they were certain of massive casualties without contributing to victory.

This wasn't the case.

Both John Keegan and James McPherson are still the most influential military historians of the American Civil War in academia. Their books do not tend to portray either Grant as a butcher or Lee as a hero bur put their actions into context.

Having said that, they do discuss Lee and to a (far) lesser extend Grant in relation to their post-war reputations. Both men's actions after the war and the lefacy of being figureheads during it have shaped the public perception until today and while not being am American myself I greatly presume that one's location will give a twist to the public perception of these generals.

I greatly suggest reading McPherson's 'Battle cry of freedom' although its density might be a deterrent.

The portrayal of Grant as a butcher and a drunk, and of Lee as a noble and tragic hero, owes much to the Lost Cause interpretation of the Civil War. The Lost Cause has been subjected to a huge amount of of historiographical study over the past several decades, so it's definitely something historians are aware of. One of the central planks of the Lost Cause narrative is that the Confederacy had brilliant fighting spirit but was doomed by the Union's superior numbers and other ignoble advantages (such as the unsporting use of black soldiers). The idea of Grant as a drunken brute, freely spending the lives of his soldiers to hammer his way to victory, fitted naturally into this story.

Another thread of the Lost Cause treatment of Grant runs through academia, via William Dunning, a very influential historian at Columbia University during the late 19th century, and his many followers. The racialist "Dunning School" of history was politically and ideologically opposed to Reconstruction, which they viewed as a project of the North to subjugate Southern whites in favor of "an unholy trinity of carpetbaggers, scalawags, and freedmen". President Grant was the single figure most prominently associated with Reconstruction, and thus it is no surprise that General Grant was not handled with much favor when the history books were written.