A friend had a copy of Roosevelt's Centurions: FDR and the Commanders He Led to Victory in World War II, and glancing at it, I came across this sentence, from one of wartime President Franklin Delano Roosevelt's famous Fireside Talks:

One of the greatest of American soldiers, Robert E. Lee, once remarked on the tragic fact that in the war of his day all the best generals were apparently working on newspapers instead of in the Army. That seems to be true in all wars.

The trouble with the typewriter strategists is that, while they may be full of bright ideas, they are not in possession of much information about the facts or problems of military operations.

We, therefore, will continue to leave the plans for this war to the military leaders.

Broadcast to the Nation on War Effort, October 12, 1942

It's quite likely that Lee actually said this (Snopes traced it a speech given in August 1874, by somone who knew Lee) but that's not the point. The point is that FDR had no problem referring to Lee, who had fought on the losing side of the Civil War, as "One of the greatest of American soldiers".

FDR also dedicated a statue of Lee in Dallas, Texas in 1936, saying:

I am very happy to take part in this unveiling of the statue of General Robert E. Lee.

All over the United States we recognize him as a great leader of men, as a great general. But, also, all over the United States I believe that we recognize him as something much more important than that. We recognize Robert E. Lee as one of our greatest American Christians and one of our greatest American gentlemen.

Remarks at the Unveiling of the Robert E. Lee Memorial Statue, Dallas, Texas, June 12, 1936

The statue came down in 2017, and now the Dallas City Council is offering it for sale.