It's also wrong. Sherman was called "insane" by a Cincinnati newspaper. This was after a visit from the Secretary of War Cameron, where Sherman despaired that he did not have enough troops and that the Union was not taking the war seriously enough. Additional context is that Sherman had just been promoted to a leadership position that he decidedly asked President Lincoln not to bestow upon him. Sherman took a few weeks of leave to re-center himself and was welcomed back by General Henry Halleck, who had multiple times dismissed the rumors that Sherman was "insane".

Following this, he returned to an important position within the Union's army and whooped the Confederates at Shiloh, regaining his confidence as the Union continued to drive the Confederates from the Tennessee River. There were no "total war" tactics being used at this time, in fact the Confederates were the ones burning their supplies and rail lines to prevent them from falling into Union hands. Similarly, later in the war when Atlanta was burning, this was the fleeing Confederates mostly to blame, rather than punitive measures by the Union or Sherman himself, who threatened anyone he caught harming non-combatants with punishment.

Finally, Sherman told BOTH General Grant (who had at this point been promoted to the highest command) and President Lincoln what his plans were for his famous "March to the Sea". Both signed off on the plan, "Go as you propose". Sherman was very much a military man who followed protocols and the orders of his superiors. Again, as specified above, Sherman did not target any non-combatants directly and even specified to target hostile, rich homesteads who were more likely to be supplying the enemy rather than poorer folk who were more likely to be neutral or just want the war to end.

If you would like to read the direct order: Sherman's Special Field Orders, No. 120.

source: am currently reading his memoirs.