How offensive is this bumper sticker?

I feel like a big dummy, but how are you guys interpreting the bumper sticker exactly?

Is the bumper-sticker/car owner saying: “if I had known that the Confederacy was going to happen, I wouldn’t have owned slaves”?

If so, then, yes, the “oh darn, I knew I shouldn’t have subjegated other human beings to soul-destroying cruelty” comes off way too blase to be funny…

What is the point to the bumper sticker? What about the Confederacy is the owner commenting on - white trash?

Sorry for my ignorance - please help me fight it.