It shouldn't be if thought of objectively...
Slavery was a legal institution in this country for over 200 years. Africans were brought here by northern slave traders to be used in northern industry, long before the antebellum South or the Confederacy ever existed. From 1641, when Massachusetts first legalized slavery, until 1865, when the Confederate struggle for independence ended, slavery was a legal institution in America that lasted over 224 years. The Confederate battle flag flew for 4 of those 224 years, but the U.S. flag and its colonial predecessors flew over legalized slavery for ALL of those 224 years yet you don't hear too many people mentioning that..
As for hate groups, they have desecrated the image of the Confederate flag in the same way they have desecrated the human race. Yes, there are people who misuse the flag, but the overall meaning of the flag as a heroic symbol cannot be forgotten because some people use it with ill intent. Hate groups also fly the American flag, quote Biblical passages, and burn crosses to promote their ideas. Should the Bible, American flag, and Crucifix be eradicated because of the fact that hate groups misuse them?
The Confederate flag represents Southern heritage, Southern ideology, and Southern pride today in much the same way it did in 1861. The only people condemning it are the people who have not a clue of what they speak.
GodlessH - Pennsylvania and California have some of the largest KKK membership numbers in the country. Are they southern rednecks? Don't use generalizations that facts cannot back up.