Well... first, before I'd get too deep into anti-Sherman condemnations, I'd want to double check if A) the quote is 100% accurate, since doctored quotes are stock in trade for some propagandists.
And B) is the context presented correctly?
Then, assuming the quote is reasonably valid, we might next notice that Sherman did correctly identify large slaveholders as the rebellion's root cause, and here speculates that replacing them with hard working small farmers, such as found elsewhere in the U.S., would prevent future rebellions.
So obviously, Sherman never read Lost Causer theses that slavery was really just the excuse, not the real cause for Secession.
As for Sherman's opinions on constitutionality of secession, Unionists have always said Confederates had no unilateral "right to secede" or to start & declare war against the USA.
And to the current location of Sherman's soul, we might remember that one of his sons became a Catholic priest and may have prayed for special intercession on his Old Man's behalf.
"Betwixt the stirrup and the ground,
Mercy I asked, mercy I found."
“Lord, lead us not into temptation”. That must include the temptation to jump into nasty spirited debates on the topics of Religion (some here seem to want a reignition of The 30 Years War) and the (very un-) Civil War. “Tied down” is a great way to describe the feeling of mud gripping our feet as people rage at each other. People who agree on so much else. Wish we could discuss things, even or especially when we sincerely disagree, without insult and invective. Those should be saved for the truly deserving lurking in the halls of government, media, and academia.
As for Sherman's opinions on constitutionality of secession, Unionists have always said Confederates had no unilateral "right to secede" or to start & declare war against the USA.
Slavery was indeed the major cause of secession (though there were others. The upper Southern states seceded because Lincoln tried to force them to send troops to invade the seceded states). But secession is not war, and the reasons for each are different. The South fought because it was militarily invaded. The union made war on the South, not the other way around. Ten thousand-plus battles, from minor skirmishes to days long heavy combat, and virtually all of them fought on Southern soil.
For the union, the purpose of the war was not ending slavery, preserving the union or nullifying the concept of secession ... it was to grind the South underfoot, to lay it waste, to dehumanize Southerners and make them the nation's trash people as far into the future as the eye could see.
Secession was not a right, it was a power; a power reserved to the states and the people:
The powers prohibited to the states are identified in Article I, Section 10, of the U.S. Constitution. Secession is not among them, so it is not prohibited.
The power to prohibit secession is not listed among the powers delegated to the United States.
The 10th Amendment states "The powers not delegated to the United States by the Constitution, nor prohibited to by it to the States, are reserved to the States, respectively, or to the people."
Don't confuse Confederates with the colonial patriots, who were indeed traitors. The difference was the type of government each sought to separate from. The crown legitimately owned the colonies and declaring independence was open treason and rebellion. The feds did not own the states (they do now); states had voluntarily entered into a voluntary union and reserved the power to voluntarily leave it.
Secession is a power reserved to the states and the people. Only in the Victor Fables does it become "unconstitutional."
Sherman's hatred for secessionists was psychotic.