I'll do anything, if I have reason to. [ which is vague, but is just clear enough to communicate his willingness for violence, if necessary. ] If I don't, I'll refuse.

[ If the objective says to kill someone, well, then he'd need to come up with a good enough reason to do it to follow through. Ample proof that advancing was actually beneficial to their cause. A sign that doing so would help him in his quest at home. And most importantly, find someone on the train that truly deserved to be killed. That'd be reason enough - maybe. But the objective by itself, just for the sake of moving forward? Right now, it doesn't cut it. ]

And yourself? You seem clever enough to surmise they may be selecting from us for some other purpose with these quests.