The Southern average citizen was defending their homeland from FedGov™ and for their states rights. You are mixing up cause and effect, again.
Just curious. What cause do you think the average German citizen was fighting for in WWII? Was it not to defend his homeland from attack? By a Red Army inarguably a great deal worse than the Union Army.
Can a man not fight bravely and honorably to defend his homeland while later recognizing that his homeland was engaged in some pretty bad stuff and that therefore its defeat was probably for the good in the long run?
I'm not trying to draw an analogy here between the CSA and Nazi Germany, except insofar as their soldiers both fought with admirable bravery and skill for (what I consider to be) bad causes. YMMV on that.
In WWII the USSR was also a bad cause, just slightly less bad than the Nazis. Many Red Army soldiers fought to defend their homeland and defeat Nazism, not because they loved Stalin or Communism.