"What possible purpose does a Confederate flag serve?"
That decision is rightly up to the states to decide themselves. Are you proposing otherwise? If so, you're not sounding too terribly conservative.
"That decision is rightly up to the states to decide themselves."
Sorry, I'm still not getting this. You're either a part of the United States or you're not. You can't have it both ways. Why would you want to fly a flag indicating you're not? By your logic, if a state wanted to fly a Muslim flag or a Mexican flag, it would be Ok, because it's "up to the states to decide."