Actually, the safest thing to do MAY be to alert the guards, but the safest thing from an INSTINCT perspective is to hold still and hope that the violence doesn't catch you. In real life, when confronted with a group violence situation, people are less likely to yell for help or help themselves than they are to just kind of freeze and go into a kind of psychological stress defense mechanism where they try to shut it out and force an assumption that "someone will make it stop".
Collective somethingorother, if I recall correctly. People getting mugged and left for dead, and nobody in the crowd does anything until one person finally overcomes the instinct and moves in to help, at which point the rest of the crowd usually breaks.
One comedian -- more of a social-commentary comedian with "real world issues" than a ha-ha comedian -- was talking about driving up and seeing an accident on the side of the road, and a guy lying there unmoving, with a crowd around him. The guy stopped and started doing CPR, and then someone in the crowd said, "No, you're doing it wrong, I know CPR, that's not how you do it." And the comedian sort of went, "So why the frell were you standing there doing nothing?!" The natural herd animal response is to cluster together and hope that the carnivores go away, even though we herd animals now have large herd animals with guns and badges whose job it is to protect us. We don't think about that, instinctively.
That is, mind you, my one psych class back in college. Actual people who know anything about psychology should set this straight, preferably starting their posts with "Tacky, you ignorant pinhead..."
Anyway. Regardless, for all that, I don't think that that's what we're talking about here. We're talking about someone who is NOT fearing for his own life, as much as he's carefully weighing his options and deciding that, while he wouldn't make an effort to kill this person of another race, he won't lift a finger, even with no threat to himself, to save them.
If there were fear, I'd probably go with neutral, but in the absence of fear (which is what I'm starting to assume, after a reread of the original post), I'd go with Step Toward Evil, although not, of course, an alignment-changer all by itself.