This fellow just chased me out of town, punching at me without a word between us.
His faction or factions are not limited to those with which I, as an agnostic Teir'Dal Wizardess who has done a lot of faction work in Halas (Cindl's Pelts, Wrath Orc Wristbands for Cindl), have become non-KoS... which are:
Shamen of Justice (they glower at me) Wolves of the North (they glower at me) Merchants of Halas (they're apprehensive, but let me buy and sell) And the Guards, themselves (who do not attack).
I don't know how the Beastlords regard me, though I've not been attacked by one of their merchants, at least. I'm not sure that means much. I've never seen a faction change for them in all the quests I've done.
I am KOS to the Rogues of the White Rose, always was, and always will be (cf. the lack of any quest with them that can be done by anyone who isn't already non-KOS, and of MOBs to kill that raise this faction).
For now, I conclude that I am KOS to the Barbarian Berserkers, as well.