Is it okay to be proud of your heritage?

I was born and raised in the south and I am very proud of my heritage. My ggg grandfather was a captain of his own regiment in the Confederate Army and I joined a confederate flag preservation group in order to help preserve my heritage. I display a confederate flag on my pickup truck as a symbol of what my ancestors fought for. They fought for freedom and peace. Why do people have such a negative attitude towards my heritage? yet, it is totally okay for blacks to be proud of their heritage? Isn't that a double standard?