That certainly is not limited to the Southern symbolism. The nature of historical memory is that it is very selective. Christianity is associated with a lot of mayhem - the crusades, witch- and heretic- burning, pogroms etc. and these are the tings that come to my mind first. But most of my Christian friends choose to cognitively bracket out these unpleasant historical facts, and instead focus on the universal and humanistic values embraced by at least some Christians. And they are right (cf. St. Thomas Aquinas or Baruch Spinoza for the starter).
When I worked as a civilian instructor for the US Army, one of my students (originally from one of the Southern states) offered me a gift at the end of the training - the confederate flag! I was quite surprised, but he explained to me that he kept this flag as a symbol of being a rebel, and he decided to pass it into the "good hands" as he was not sure where the next assignment was going to be. At that time, the NFFE local (the union federal employees) of which I was a member put a fierce fight with the management and I was one of the most active players in that fight. Many (if not most) of the trainees hated their bosses - both military and civilian - and supported our side- which explains the gift.
I did not display the flag in or near my house - putting up ANY national flag is more than my stomach can handle - but I kept it in a safe place through my endless moves from place to place. Unfortunately, it did not make it to the East Coast - it got lost in someone's garage where it was temporarily stored together with my other possessions and memorabilia (which also vanished). But it made a really nice and valuable gift - certainly more memorable than most commercial products passed to me in the form of presents.
Wojtek