Brilliant argument, my friend! Simply brilliant! (Of course, one might just as well argue that the war was fought simply to kill Americans: '600,000 living Americans before the war, 600,000 dead Americans after!' ;>)
The gist of many secession-defenders, like you, is that the north didn’t care about slavery only using it as a pretext to use freed slaves to fight for them. Then answer me, why didn’t the north allow slavery to be reinstituted at war’s end, huh? Stop the evasive answers and answer that one simple question.