Indeed. The rebels initiated hostilities against the United States even before Lincoln assumed office.
Well sure. After some military people spike and burn a bunch of their cannons, kidnap a ships captain and force him to carry them over to a new unfinished fortress where they seize control of it, and then threaten shipping and the local town, you can't blame them for initiating some hostilities back.
But if Anderson hadn't started the hostilities, there would not have been any hostilities.