The rationale for succession had slavery as a primary factor, but the war was fought for the right of States to leave the union if they wished. Federalism and states rights sentiments are tied up with the symbol of the flag, though it might be more accurately framed as anti-federal government than pro-state government. Importantly though I'm not denying that there are also those who use the flag as a symbol of racial animosity, nor are the two groups completely separate.