The best essay ever written on that topic: A Nation of Cowards
Excerpts:
Crime is not only a complete disavowal of the social contract, but also a commandeering of the victim's person and liberty. If the individual's dignity lies in the fact that he is a moral agent engaging in actions of his own will, in free exchange with others, then crime always violates the victim's dignity. It is, in fact, an act of enslavement. Your wallet, your purse, or your car may not be worth your life, but your dignity is; and if it is not worth fighting for, it can hardly be said to exist.[snip]
It is impossible to address the problem of rampant crime without talking about the moral responsibility of the intended victim. Crime is rampant because the law-abiding, each of us, condone it, excuse it, permit it, submit to it. We permit and encourage it because we do not fight back, immediately, then and there, where it happens. Crime is not rampant because we do not have enough prisons, because judges and prosecutors are too soft, because the police are hamstrung with absurd technicalities. The defect is there, in our character. We are a nation of cowards and shirkers.
[snip]
One who values his life and takes seriously his responsibilities to his family and community will possess and cultivate the means of fighting back, and will retaliate when threatened with death or grievous injury to himself or a loved one. He will never be content to rely solely on others for his safety, or to think he has done all that is possible by being aware of his surroundings and taking measures of avoidance. Let's not mince words: He will be armed, will be trained in the use of his weapon, and will defend himself when faced with lethal violence.