I would be proud to find Confederate soldiers in my ancestry, just as I would if I found Union soldiers. It is history, for Pete's sake!
On the other hand, my husband's mother is a New Jersey farm girl whose progenitors fought for the Union (at least the ones who had gotten here from Ireland already) and nobody around here holds it against him!
Actually, one of my ancestors was from New York City, and a bunch of his family stayed up north, so I probably have some cousins I don't know about who fought for the Union. I also had an Englishman ancestor who immigrated in the 1810s, to Newark NJ, with his father and brothers. A bunch of them stayed up north too. He moved to Alabama and did own slaves for a time, but sold them as he decided it was too much trouble and responsibility.
The historian Eugene Genovese said that slavery would have fallen of its own weight within a few more years, as mechanization and improved farming techniques made it completely obsolete.
I don't really care, other than as a historical interest. The columnist is obviously suffering from LGS (liberal guilt syndrome), in which you feel obligated to feel guilty about something you didn't have anything to do with, while feeling no guilt about bad things you do.