Justifying self-defense is called into question only when thinking of physical defense. When it pertains to ensuring our physical well being, our actions are scrutinized much more carefully than at other times. The use of violence is at the root of this issue.
The ethical issue of using violence can be based on the ethos of the people involved. This guiding belief is a result of a nation’s or culture’s worldview. Belief in a supreme being can cause a different worldview than a humanist one.
Protecting the innocent is a worthy outcome in either case. Those who harm others, whether individually or as a group or nation, are widely reviled when they are the aggressors. Actions against such people are generally seen as justifiable when the actions are used to end the situation.
To be deemed truly innocent, the defender must be recognized as one trying to end the conflict, not as the originator or abettor. In the case of a home invasion, it must be clear that there is an attempt to rob or do bodily harm. Different areas consider the right to defend in these instances a bit differently. One cannot use lethal force if the culprit for getting away with something, unless they remain actively engaged in doing harm. Some states have a “Stand Your Ground” philosophy and are more lenient regarding the use of deadly force, though the value of property is not place above human life. This considered vengeance, not self-defense.
Some believe all physical violence is wrong, regardless of the reason, sometimes citing Exodus 20:13, “Thou shalt not kill.” (Newer translations refer specifically to murder, not killing.) There is no scriptural prohibition against “justifiable homicide.” When it can be defended ethically, deadly force is neither illegal nor immoral.
Nevertheless, defending oneself must be proportionate to the potential harm of the threat. This can vary widely, but you do have a legal and inherent right to defend yourself when being threatened or attacked.