Don't get me wrong - I find the idea of waving a confederate flag around basically repulsive. I am not "proud" of slavery in my family. But I am proud of the achievements of my southern ancestors (most of whom were not slave owners). Heck, I am even proud of one particular slave owner, because of his excellent treatment of his servants (black and white - many of which he freed and gave land to), who were also very loyal to him and to his family.
Their descendents to this day have a close relationship with our family, with both families attending weddings, funerals, holiday gatherings, etc. with each other. My family continued to employ members of that family, well, actually to this very day.
One of my father's closest childhood friends was from that family - both boys were the same age and grew up together playing on the farm. His mother and grandmother and great grandmother - all the way back - worked willingly and happily for my family, and she was like a second mother to my dad and grandmother to me. Our families are entertwined together for many generations.
Some of my fondest memories are of sitting in a big sunny kitchen watching Julie whip up a chocolate cake and waiting for the spoon to lick. I remember my dad stomping into the kitchen in muddy boots and Julie turning around to him and hollering, "Get yore scrawny rear end out of my kitchen in those boots!" and "hitting" him with a dishtowel, and I remember my dad's shamefaced look as he mumbled, "Yes m'am, I'm sorry!" and ducked out the back door.
Southern heritage is not just about slavery. In fact, the vast majority of southerners who are proud of their heritage are not descendents of slave owners and are not proud at all, or supportive, of the institution of slavery. What they are proud of is a legacy of strength, independence, honor, graciousness, and bravery. Settling the southern US wasn't easy, and most southerners and their ancestors didn't grow up sipping mint juleps on a plantation house veranda. Most were dirt farmers carving out a living for their families with their own muscle.