He could have begun his eternal war in Ohio, where because of its history of slave ownership, no war crimes could be committed.
Ohio outlawed slavery in 1803. John Brown was born in 1800 and his family moved to Ohio in 1805. So, any slaves he saw in Hudson (which is outside of Akron, I believe) would have belonged to slave owners from another state who were passing through Ohio at the time.
From an article on line:
"Free African Americans and slaves had lived in Clark County, Ohio since the early 1800's. The Northwest Ordinance of 1787 banned slavery in the territory, however, slave trading and slave holding continued until 1830 with the support of the courts. This is evidenced by the prosecution and fining in 1812 of James Demint, the founder of Springfield, in county court for paying some African Americans for work they did around his place instead of paying their owner John Kenton. John Kenton was the brother of Simon Kenton, also reported to have owned slaves (Kinnison: 1985).
"In Ohio, Clark County was settled mainly by two groups of people from the pro-slavery state of Virginia. The first group to arrive in the area were antislavery. With the settling of the area more Southerners followed, many pro-slavery bringing their slaves with them. Many freed their slaves after entering Ohio. Some slave owners did not free their slaves until 1830 when the Ohio Legislature required it."
So, it would seem that slavery did exist in your state beyond when you think.
Sherman could have burned Columbus under the same rationalization you accept for Atlanta.
Thought you were someone else, and that comment about applying to your state was intended for Ohio.