Lincoln showed that a Southern slavery empire was impossible. That was good, especially for non-slaveowning Southerners of both races.
Mechanization would have shown the same thing.
I sure can understand the complaints about taxes. ;-) Yes, taxes are a nuisance. But, enslaving people is far, far worse.
The last thing that goon wanted was a bunch of freedmen running around the new territories. Get real. Your hero was a racist to nth degree.