For many in the south, it's not at all about a cause. I think that's why there is such a massive disconnect on this topic. Some people absolutly use it to spread hate. Some to signify the rebel life style, and others it does represent tradition, culture, pride ect. People who live in the south, especially those with long family histories are talking about their families histories and the traditions they hold dear and how the flag is a representation of that, because it has been for 150 some odd years.

During the war it was a rally flag for for the south, all of whom were fighting (rightfully or wrongfully) to defend their way of life. Even though the rich and powerful were all about slavery, Remember, a vast majority of families owned no slaves. Those families, probably would have liked to own slaves, but do you think they really went to war for 4 years and died horribly for something most of them would never own?

More recently the flag was used by hate groups to spread fear. Because of groups like the kkk the battle flag has an extremely negative connotation in many people's eyes. Like many have said before, before the 1950 almost no one flew the Confederate flag. It was not until the kkk and others popularized it that it became public. There was actually a group called the Daughters of the Confederacy (I think?) Who were very active up until the mid 1900s defending the proper (respectful) use of the flag. If it's the same group as the one I Googled, they are still active trying to defuse the connection with the flag and the hatred that has grown up around it.

TLDR: the problem with flags is that they are powerfully symbollic, and can be valued differently by different groups. The battle flag specifically holds LOTS of different values and that is why it's so controversial.