Oddly, had Davis and the Southern government thought as you did, that revolution was a 'winner take all' scenario, the war would have likely ended with the capture of Washington and the slaughter of the black Republicans after the war's first major battle. It seems, then, from that perspective, that the South's willingness to let the North go it's separate way probably cost them the war.
No, we are speaking of Revolution in a political sense, the right of a people to change a gov't when real tyranny exists which cannot be rectified by any other means.
The means of fighting a revolution to not have to include full scale slaughter, as the South did not did not receive that treatment, they being allowed to return to the US upon taking oaths of loyalty (which most did)
As for taking Washington, it wasn't for want of trying.
I think Lee got stop twice did he not?