Peetzakilla -
I wouldn't expect you to give your life to save someone from being mugged. If you are completely unprepared to defend someone, then I guess all you can do is hide.
But, how can you consider yourself prepared to defend yourself and your family if you are unprepared to defend a stranger? If you are carrying a pistol, a knife, a cane, etc. and you are confident you can protect your own in a deadly situation, are you not confident you could protect someone who is unable to defend against the threat? Or are you saying that you are confident in your means of protection but would rather not get involved in someone else's problems? If that is the case, than I think you are missing a moral benchmark just as badly as the "defenseless" victim is.
Or perhaps you would better understand my point with an analogy: You're driving in a snowstorm with your family. You pass a vehicle buried in a snow bank and can clearly see people in the vehicle unequipped to fix their situation on their own. Yes, these people messed up badly by not having an emergency plan. But did you yourself bring an emergency kit for your family's needs, or are you in no better a preparedness situation than the people on the side of the road? And if you did bring a kit, are you going to ignore the plight of those people because they are strangers, or will you help them because you can?
I'm not saying everyone should get a handout regardless of whether they deserve it. But a functioning society necessarily depends on people willing to act to correct a danger to that society, even if it is not a danger to the person himself.