Such as? What are those examples?
Is there a reason you feel the need to put scare quotes on celebrate and Southern heritage? Are they not allowed to have a heritage?
I don’t want to defend the flag, because the Confederacy was a monstrosity. But I also don’t like seeing people that have never met a Southerner in their lives (not necessarily you specifically, but certainly most people attacking it) thinking they know all about it and all about the people that fly it.
There are ample numbers- by no means a majority, but certainly a large number- of Black people that use the flag because, whatever its flaws and whatever evils committed under it, that flag is the most popular symbol of Southern culture- their culture.
That’s another factor; most people insulting the South don’t realize just how much of their attacks land on Black people themselves.
Those who want to "celebrate" their Southern "heritage" have plenty of symbols and flags to choose from that don't have inherently racist and treasonous implications.