Not all Southernors were/are democrats. The Confederate flag may mean one thing, and one thing only, to you, but for some it encompasses an entire heritage.
Most of us honor our heritage, even though none of our ancestors were perfect. Today I honor my Dad. If the only thing you knew about him was his biggest flaw, you might be offended by my respect for him, as you are by Southernors’ respect for their fathers.
Some may have protested the abuses, nonetheless they still got ran over by the North in the Civil War.
Proximity works unwanted effects sometimes.