I agree with Acme when she wrote 'Barnacle may have discussed why generals decided to fight for the south; that has NOTHING to do with why statues were up up 50-75 years later.' but for the sake of this discussion it's worth noting that Robert E. Lee was a wealthy slave owner by marriage and by some accounts a brutal one, so it's reasonable to assume that his motivation for accepting a commission in the CSA army exceeded just the defense of The Old Dominion. His preference for his home state over the United States is another component in the myth of the "Glorious Lost Cause".

I couldn't begin to articulate the argument nearly as well as New Orleans Mayor Mitch Landrieu so here is a speech he gave explaining the removal of Confederate monuments in his city. Incidentally, I found it at billmoyers.com, an excellent source of information:

billmoyers.com

Excerpts:

"The historic record is clear: The Robert E. Lee, Jefferson Davis and P.G.T. Beauregard statues were not erected just to honor these men, but as part of the movement which became known as the cult of the lost cause. This "cult" had one goal: through monuments and through other means, to rewrite history to hide the truth, which is that the Confederacy was on the wrong side of humanity. First erected over 166 years after the founding of our city and 19 years after the end of the Civil War, the monuments that we took down were meant to rebrand the history of our city and the ideals of a defeated Confederacy. It is self-evident that these men did not fight for the United States of America. They fought against it. They may have been warriors, but in this cause they were not patriots. These statues are not just stone and metal. They are not just innocent remembrances of a benign history. These monuments purposefully celebrate a fictional, sanitized Confederacy, ignoring the death, ignoring the enslavement and the terror that it actually stood for."

"After the Civil War, these statues were a part of that terrorism as much as a burning cross on someone's lawn. They were erected purposefully to send a strong message to all who walked in their shadows about who was still in charge in this city."

"And in the second decade of the 21st century, asking African-Americans — or anyone else — to drive by property that they own, occupied by reverential statues of men who fought to destroy the country and deny that person's humanity seems perverse and absurd. Centuries-old wounds are still raw because they never healed right in the first place."

"The Confederacy was on the wrong side of history and humanity. It sought to tear apart our nation and subjugate our fellow Americans to slavery. This is the history we should never forget and one that we should never again put on a pedestal to be revered."

Well worth reading or viewing if you're interested in this issue.

Also, I totally agree with Stu's statement "Their artistic merit is irrelevant to the discussion."
If people want to appreciate what they see as their "esthetic value", indeed, put them in museums but get them the hell out of public view for all the reasons Mayor Landrieu mentioned in his speech. I'd prefer to see them torn down and recycled into something useful.

Here is a timeline for Confederate monument and statue building between 1870 and 1980 (source-SPLC):

Mother Jones

and here is the article in which it appeared:

Mother Jones