Why do some northerners (USA) fly the Confederate flag?

I'm from GA and I heard that some northerners (like in Wisconsin and Michigan) fly the flag. That seems weird to me because people here fly it because they see it as a symbol of the South and we are very proud of our southern culture. People up north obviously have a different culture than us and I also thought a lot of them seen it as a hate symbol. So why do some people above the Mason-Dixon line do that?