The Lost Cause was a Bad Cause
The tacit understanding after the close of the Civil War was that the legacy of "The Lost Cause" would be honored. Its leaders were to be acknowledged as honorable - not traitors - and identification with the Confederacy would be compatible with American patriotism.
That understanding is breaking down.
In spite of what revisionist historians and neo-Confederates would have us believe, there would not have been succession without slavery. Certainly, that isn't the only reason people fought, but it is disingenuous to not see it as the central factor that almost destroyed the Union. Further, since the end of the war, the symbols of the Confederacy have been identified with segregation and racism.
That is not to say that Southern nationalism equates with bigotry or that there aren't aspects of regional identity worth fostering. During the war people, most of whom didn't own slaves, defended homes and families - and were heroic. But neo-Confederate attempts to deny that racism is part of the fabric of Southern memory is not honest. (Not to say that the North didn't and doesn't have its share of sins-but certainly by the end of the war, the the U.S. Flag was the flag of emancipation.)
The South needs to own up to its history - good and bad. Bigotry against Southerners is as loathsome as any other prejudice. Everybody has a right to celebrate what they are - but specifically Confederate symbols need to be eschewed. The South had symbols long before succession - and those symbols should be the ones used both now and into the future, celebrating what is best in the American character.
If you want to fly a rebel flag, consider using the original - the U.S. Flag.