The emotional aspect of Leftist political critique is not, in total, a positive thing. And it has a tendency to bleed into some backward political positions, such as an ambiguity over the Civil War (see Howard Zinn). Because we on the Left tend to root for the underdog, this too often translates into a weird support, or waffling in condemnation, of the South. This support is usually camouflaged as saying that the war was unnecessary and that the slaves could have be freed through some repurchase mechanism. (Except, of course, this was tried numerous times and was always rejected.) Therefore, under this 'Left' critique, the Civil War was just a battle between ruling class factions, with the North representing the rapacious Northeast financial elite.
The realty is the South needed slavery, they wanted to expand it, and they were imperialist force with eyes to the Caribbean.
And, it is my opinion that the much reviled Sherman should be celebrated. For what ultimately needed to happen was for the Southern aristocracy to have their back broken. Instead, they were coddled, and Blacks were dealt with another 100 years of state sponsored terror as the Northern armies evaporated. And this reactionary force in American life has never gone away -- the split between right-to-work and closed-shop states is but one manifestation up to the present time.