Okay folks, help me clear something up.
Between Peace Talks and Battle Ground, we know something is clearly up with McCoy. His behavior is erratic, he feels justified in taking extreme actions, etc. He and Harry clash over lots of things - especially vampires. But something feels off about the order of operations, so to speak. Eb at the end of Peace Talks cuts loose like we've never seen. And yet in Battle Ground, his behavior toward Harry is reset to more closely resemble the Hounds of Tindalos encounter. Yeah there is some animosity between them, but unless I am missing something - no further mention is made of the dockside encounter in their dialogue, only in Harry's thoughts.
So here's my theory - The McCoy from the end of Peace Talks has time traveled to be there from some point after Battle Ground. (Aren't Hounds of Tindalos drawn to someone who has time traveled, and isn't breaking the Laws of Magic within the purview of the Blackstaff?) Some event in the future precipitated McCoy to try to neutralize Harry at that crucial point in time - how else would Eb know to look for him at the docks.
So that's my WAG. Can anyone work up a logical progression of Eb's behavior from the beginning of Peace Talks on? I have trouble accepting that the Eb on the roof of the BFS is the same Eb who mere hours previous attempted to kill his grandson. Have only read BG once a couple months ago, so may be forgetting important things.