The moral duty not to harm others is one the greatest moral standings of all the time. The greater good for triumphs the lesser good and as such, some actions are not permissible for the sake of the greater morals. However, such may not be applicable all the time. How does this situation arise?
If the greeter moral standing of not harming any one is upheld by all the people, there shall be no situation that would require one to protect a child or to self-defense of any sort. Such occurs since no one would harm or at least anticipate harming another person. In such a situation then, the greatest moral standing remains valid. The validity is limited to universal application that is devoid of any ambiguity either in the process or in existence of contradicting morals. But is this the situation in the world?
Owing to the fact that humans are inherently competing for natural resources, such as land, water, jobs, and other material gains, or even for political power, they engage in fights, get into disagreements that lead to the compromise of the greatest moral duty of not harming each other. For example, a society made of a few rich people with the majority poor does not only lead to conflict, but it is harming the people indirectly. If the rich man forcefully takes that belongs to the poor, the poor has a right to fight for self-defense. It is on same grounds that an individual can protect the life of an innocent person or child from any harm. But when is someone presumed innocent? Some situations can be very tricky especially if the person presumed innocent is not indeed innocent. Therefore, one has to take precaution not to harm the innocent who are fighting for self-defense. In this respect, therefore, one has to apply wisdom so as not to misuse action or in action leading to unnecessary harm (Stanford Encyclopedia of philosophy, 2014).
References
Stanford Encyclopedia of Philosophy (2014). Ancient Ethical Theory. Retrieved on November 5, 2014 from http://plato.stanford.edu/entries/ethics-ancient/