It's just a symbol of identity or culture, like most flags. There's a massive cultural difference between the rural south and the highly populated coastal cities. The flag to many is a symbol of that difference, and has many of the psychological undertones that makes the "don't tread on me" flag popular, mostly a willingness to push back against external influences.
And there are a lot of people outside the South who do show and like the Confederate flag.
So while I agree that it's a symbol of an identity and culture, I don't think it's a geographic regional identity and culture.
I think you're arguing in good faith based on your own experience, but I would gently suggest this is an opportunity to consider a wider variety of data and perspectives.
I mean, it's not like I'm wholly unsympathetic to failed secessionist states and their symbols/paraphernalia. People still use the flag of Biafra where I'm from, after all. But those that do are self-aware enough to acknowledge/be upfront about the values they hold and the message they pass when they use it (it certainly helps that Biafra attempted to secede in response to ethnic tensions/discrimination, not because it wanted amongst other things the right to keep slaves).