In this editorial, I would argue that the actions of Sherman's own troops were justified.  I would argue that, so long as the war was justified, Sherman's actions were too.

Sherman's actions were no different (and considerably less deadly) than the bombing of various Japanese and German cities in WWII.  The whole point of what Sherman did was to break the South's will to fight and its ability to supply its armies.  This is a valid thing to do in war.

In war, cruel things happen.  They are done to try to end the war more quickly.  This is what Sherman was doing and his actions were therefore justified.