Given his very recent treatment of her, it did seem kind of strange for Barnabas to care if Lang shot Julia. Though obviously aware of her feelings for him, it seems that up to this point, Barnabas was only using them to manipulate her for his own ends, such as securing her silence about the experiment, and getting Willie released.
But perhaps Barnabas' feelings were undergoing a change without his even realizing it. In todays episode, when the experiment is starting and he tells Julia he is glad that she is there is the first time I sense genuinely warm feelings towards her on Barnabas' part. A simple, yet very touching scene.
