Rule #1: Anyone's first duty is to protect themselves.
Rule #2: Anyone with family who depends on them (i.e. spouse and/or kid(s)) has a duty to remain alive and in a sufficiently good condition (physically, mentally, emotionally and legally) to be able to get up in the morning and go to work.
Rule #3: Anyone who has the slightest bit of decency has, IMHO, the duty to save the life of another person (or prevent serious bodily injury from occuring to them) if possible - i.e. if you don't violate rules 1 & 2. If I can reasonably, and with ample legal justification, stop an assault that is either deadly or obviously about to become so, I sincerely hope that I will do so - as long as the risk of making my wife and kids a widow and orphans is not too high. Of course, one can always take the view that you could be the next target of the goblin in question, so that acting on behalf of another person is an indirect means of self-defense.
I prefer to act in such a way as to be able to look at myself in the mirror and not be ashamed of the person I'm looking at. I would be very ashamed if I had the ability to save the life of an innocent person without undue risk to myself and, instead, didn't lift a finger (or a .45).
Regarding the politics of the victim - this is irrelevant to me. If it is a moral issue (in addition to a practical one), the only thing that matters is whether you can do something about saving the life of an innocent person. Besides, saving the life of an anti with a gun may turn that person into a pro-gunner (or at least make them neutral). That's no reason to save someone, but it would be cream on the cake.