Their restrain did not save the South from the destruction that was visited upon them in the name of "Justice". If the north got mad about the burning of their cities, could the south have losted anymore than they did?
If I am not wrong the Lee family was some of the first victims of Northern aggression with the occupation of Arlington in violation of the 3rd Amendment: to wit; "No Soldier shall, in time of peace be quartered in any house, without the consent of the Owner, nor in time of war, but in a manner to be prescribed by law."
Does anybody know what "Law" was passed to allow the occupation of private homes, even those of the enemy, during the war? After the war the Lee family won their civil suit and restitution, I believe a $180,000 settlement, against the United States Government for the confiscation of Arlington on this very fact.
Also the burning of George Washington's home at White House, Virginia, during the Penisular Campaign, which was the home of Mrs. R.E. Lee at the time. It was in fact under a protective order from General McClellan but burned under Mysterious circumstances during the Federal retreat during the Seven Days Battle.
So if anyone had a personal reason to burn Gettysburg to the ground it was Lee.