“Heritage” in this context is a white supremacist codeword for “the southern states should never have been forced to give up on slavery”. Statues of confederate leaders, incorporation of confederate flags into later state flags, etc. were (and still are) part of a large-scale campaign to promote and defend segregation and racial inequality and injustice, explicitly intended to intimidate and disempower southern blacks.

You can easily find (racist white) people displaying the confederate flag in northern states, but you will be hard pressed to find any black people in the south who feel regional pride toward confederate symbols.