When I was a lad, they used to print his birthday on calendars, along with those of Washington, Lincoln and even Confederate Memorial Day. Lee believed that the North was trampling upon the rights of the states. He was conflicted in his loyalty to the US and to the state of Virginia. He said he never hated the North and prayed for them every day. In a letter to his oldest son, in January 1861 (emphasis mine):
The South, in my opinion, has been aggrieved by the acts of the North, as you say. I feel the aggression, and am willing to take every proper step for redress. It is the principle I contend for, not individual or private benefit. As an American citizen, I take great pride in my country, her prosperity and institutions, and would defend any State if her rights were invaded. But I can anticipate no greater calamity for the country than a dissolution of the Union. It would be an accumulation of all the evils we complain of, and I am willing to sacrifice everything but honor for its preservation. I hope, therefore, that all constitutional means will be exhausted before there is a resort to force. Secession is nothing but revolution. The framers of our Constitution never exhausted so much labor, wisdom, and forbearance in its formation, and surrounded it with so many guards and securities, if it was intended to be broken by every member of the Confederacy at will. It was intended for "perpetual union," so expressed in the preamble, and for the establishment of a government, not a compact, which can only be dissolved by revolution, or the consent of all the people in convention assembled.
It has been said that the Civil War was essentially a grammar lesson:
The United States is, versus the United States are.For men like Lee, the war wasn't about preserving slavery, it was about upholding principle. There is a mindset that seeks to erase such men and every trace of them from history, rather than try to understand them. There have been flawed individuals, throughout the history of America, up to and including the current President. We gain nothing in attempting to whitewash history, or erasing the past.
Happy birthday, General Lee!