There were three Confederate flags, none of which are the flag we see flown today. People believe it is a symbol of racism simply because it has been used by the KKK and other less than reputable groups. Southerners should take pride in the real flags as a historical reference of the battle fought by their ancestors (not just about slavery). It is part of Southern heritage for both white and black people and should remain in place in public settings as a memento of war over economics and politics.
Images of the real flags can be found here:
https://en.wikipedia.org/wiki/Flags_of_the_Confederate_States_of_America