OK, let's go through this slowly ..........
Your "heritage" that you are so proud of, and wish to retain, is based on denying the rights enshrined in the Declaration of Independence, and the US Constitution. The Confederacy of which you are so proud was based on the proposition that the black man was not the equal of the white man, and that his natural state was subjugation to the white master race. The wealth of the South was built on the backs of an enslaved people, and justified by the Christian church. And since blacks were considered to be sub-human, there were no limits to the cruelties that could be imposed on them ...... and justified as for their own good.
Even after the defeat of the confederacy, racism, discrimination and hate has been endemic. The birth of the KKK (whose proudest symbol is that of your beloved flag), segregation, discrimination, Jim Crow laws .... let's not forget lynchings and burning burning blacks alive - or perhaps you have not seen those photographs, with the symbol of your heritage proudly and prominently displayed ?
Why should it be necessary to explain why that flag is a symbol of slavery, oppression, and racial violence ... but hey, that's your heritage. If you want to fly that flag on your front lawn, or your house, or on your car or clothing, that is certainly your right to do so.
For that same flag to fly or be displayed at a government building is just plain wrong. Tell me, do you see Nazi flags flying at German government buildings ? No, and for exactly the same reasons that the Confederate flag should not be a part of any US government building.
Again ..... no one is trying to take away your right to display your heritage on private property or on your clothing. But for government to be seen as approving the actions of the Confederacy, and condoning the slavery and oppression it prized, is wrong. Read the history books .... the south lost, slavery is a bad idea. Not a difficult concept. If you want to be proud of your heritage, you need to find something in your heritage that does not negate everything the US stands for.