Something I find odd is that, as The Doctor pointed out partly above, there were a number of Confederate flags flown during the war, none of which are the Confederate flag that is currently pushed to be included in Southern state capitals for historical reasons.

As The Doctor said, the modern "Confederate Flag" was in fact not the Confederate States' national flag, but was only the battlefield flag of Gen. Robert E. Lee's Army of Northern Virginia.

Here are the MANY different flags of the Confederate South:
https://en.wikipedia.org/wiki/Flags_of_the_Confederate_States_of_America

This one in particular makes the argument against its inclusion in state capitals, as an inherently racist symbol, as clearly stated by the guy who created it:

 Quote:
The flag is also known as "the Stainless Banner" and was designed by William T. Thompson, a newspaper editor and writer based in Savannah, Georgia, with assistance from William Ross Postell, a Confederate blockade runner.[1][2][4][5][6][7] The nickname "stainless" referred to the pure white field which took up a large part of the flag's design, although W.T. Thompson, the flag's designer, referred to his design as "The White Man's Flag".[1][2][3][4][5][6][7] In referring to the white field that comprised a large part of the flag's design elements, Thompson stated that its color symbolized the "supremacy of the white man":




Second national flag
(May 1, 1863 – March 4, 1865[17]), 2:1 ratio

Second national flag, also used as the Confederate navy's ensign, 1.5:1 ratio

  • As a people we are fighting to maintain the Heaven-ordained supremacy of the white man over the inferior or colored race; a white flag would thus be emblematical of our cause.

    —William T. Thompson (April 23, 1863), Daily Morning News[1][2][3][4][5][6][7]


But again, this is not the Army of Northern Virginia battle flag widely advocated for, and again, I doubt many who advocate for the flag are aware of these ideological origins, or would support this ideology.