I sympathize with your misconceptions on the issue.  I too spent time growing up in the south.  You are faced with northerners, many who's roots don't really have a part in the issue, who treat all the southern past as evil. You react defensively with what you've been taught. 

Now we have the modern age of google and legitimate historical references. You've probably been told slaves were treated well as valued property, a common line, but not true.  You've probably been taught that slavery would die out, but the laws were moving in the south to insure its survival.  

Believing Dred Scott is believing that black people weren't human.  The VP of the confederacy said its cornerstone was:  "the great truth that the negro is not equal to the white man, that slavery, subordination to the superior race, is his natural and normal condition."

I will agree that slavery was not the total cause of the civil war, but it was totally an evil institution with no merits or positive end game.