There are always going to be people that believe that the reason for the Civil War was slavery, and that the Union Army was on some Holy Crusade. Nothing that anyone is going to say is going to change their views. I am certain that others have a romanticized view of the South, too. Nothing anyone is going to say is going to change their minds.
The very people that are most interested in this subject are most likely the worse ones to trust. They tend to be emotionally involved and see things through their own spectacles.
Of course Hurlburt was biased. But the accounts of Sherman's actions were biased too. Almost every contemporary account had an ax to grind and must be taken with a grain of salt. But there's enough evidence beyond this book to show that Hurlburt was on to the truth. There is evidence that the elderly paralyzed Levi Trewhitt was thrown into a Confederate prison without due process for polittical reasons where he died. There is evidence that Confederate Congressman William Tibbs was an aggressive slave trader. There was evidence that Fantroy Carter was murdered by Confederates. There is evidence that the Tennessee Confederate state government systematically violated the 2nd Amendment by their gun confiscation scheme. Hurlburt does not relate any unknown themes, but merely details the already revealed ugly face of Confederate despotism.