BTS stills are great for promo, and production packages, etc. Not essential, but pretty good. Not worth getting tied over a barrel for, though.
So the dude was originally brought in to do stills for one of the actor's publicity? It suuuuure would suck if that actor's publicity stills were suddenly 100% unusable for the actor, 'cos his friend is being a douche. You have some claim over the content of the photos, right? I mean... if you can't use them, maybe that photographer can't, either.