Although I realise it is largely a matter of opinion rather than fact as to what was the primary reason behind the civil war it is a matter of record that when the war began abolition of slavery was not one of the stated goals. See highlight below.
The idea I put forward that there was an element of 'punishment' behind the abolition of slavery is reinforced by the highlighted passage below
In fact the single biggest factor in setting the stage for the civil war appears to have been the war with Mexico and the ensuing political wrangling over the new territories won. The southern states feared the loss of it's natural majority in congress and the senate to the industrialised north who were at that time pushing their own brand of social structure and democracy. (which is proof of the saying 'those who don't learn from history are condemned to repeat it'