Heroics my ass. The coach is full of crap on this one.
The issue is far more complex than just slavery. The war did not have to happen. The rest of the western world did away with slavery without having a war. Compensated emancipation was a viable option at the time. However, ignoring the constitution and imposing policy with military force allowed Lincoln to solidify central federal authority over that of sovereign states.
You are correct, the war did not have to happen. But firing on a Federal Fort and issuing Letters of Marque against U.S. flagged merchant ships are acts of war authorized by Jefferson Davis.