Many men believed they were fighting for their right to remove themselves from the Federal government which they felt had become tyrannical.In order to fully understand the reasoning of the South, you have to step into their shoes. Back then the US was thought of much as we think of the UN, a group of nations (or states) that were united. So if several leading nations in the UN were to tell us to do something that we thought was infringing on our rights, what would we do?
Another plagerization:
The main cause of the Civil War was States Rights. The South was afraid that Abraham Lincoln would emancipate slaves, and they believed that the US President should not be making decisions that affected the entire country and that States should have the right to make those decisions. It wasn't so much the emancipation of slaves that concerned the South, but rather the fact that if Lincoln were to free the slaves, it would be denying the states their rights.
How do you suppose that rationale works when it was the slavers who largely controlled the federal government?