There is truth in the point that the North had no intentions of freeing the Slaves as the objective for the War. The North was already planning to build Rail Lines and Rail Heads to ship the raw materials from the South to the North. They also planned to raise tariffs and taxes, from approximately 18% to 40% on all imported goods. Because the South basically imported most of what they needed from Europe, while the North did not, this presented a real problem for the South. This would cripple many owners and allow for the North to simply use Rail Lines to just bring the raw materials needed to a ready made work force to the North. Because so many immigrants were arriving daily in the North, a dirt cheap work force was available to the North to process the raw materials into goods very cheaply. The next logical step would be to buy out the plantation owners for pennies on the Dollar. This would effectively bankrupt the South.
I don't believe that anybody would argue that Slavery was a good thing. Everybody knows it's wrong but the North was just as guilty of this as the South. The North did not free the slaves until after the War had started and even then, they didn't free the Slaves in the North. They only freed the Slaves in the South. The Slaves that they couldn't really grant freedom to in any case. They wanted to use this as a tool to further weaken the South by encouraging Slaves to run away. I don't view the War as a War over Slavery, per say. I see it as a power play by the North against the South for raw materials. If you study the history of immigrants to America, they were not much better then the life of a Slave. Conditions for them were horrible so the North, IMO, was not nearly as idealistic or noble as history sometimes depicts. It was about money and greed IMO. The South had no intentions of letting their work force go because it would mean losing their entire way of life. Was their way of life wrong? That is a different argument IMO but the reality is that the South, and really the North as well, was built on it. The difference was that the North developed much more quickly and had more people available to develop an industrial economy. The South had far fewer people and had little choice at the time. Again, not talking right or wrong here, just presenting the realities of the times.
If you think about it, it would have been much smarter and cheaper for the South to simply abolish Slavery and just pay it's work force to do a job. I mean, if you think about it, that's a good business practice right? You simply raise the price of your product and pass it on to the consumer. Who was the consumer? Overwhelmingly, it was the North. The North had no intentions of paying more and, IMO, they saw an opportunity.
This is what really caused the Civil War. Slavery, IMO, is just a bye product of the actual cause but, it was a good bye product. Sometimes you get lucky.