How did threats to the southern identity lead to the secession of the south?

When South Carolina seceded from the Union in 1860, the main justification of secession was that southerners believed secession was the only way they could preserve their institution of slavery. Not all southerners supported secession, however, but those who did argued that because the southern states were a part of the Union, their rights should be respected by the federal government.

The answer is installation.