I doubt Lincoln would have had the support of many states for war if South Carolina had not fired on a Federal installation or other states hadn't seized Federal property. So your the South did it peacefully argument I think is false. However its interesting to speculate what might have happened had the South allowed the Federal installations to exist and waited about a year or two as a cooling off period and exercised patience and just let the passions die down a bit. Perhaps lacking enough support for War Lincoln would have been forced to compromise. Firing on Ft Sumter gave Lincoln all the excuse he needed to go to war with the South because it galvanized Northern public opinion.