"The necessary consequence of man’s right to life is his right to self-defense.
In a civilized society, force may be used only in retaliation and only against those who initiate its use. All the reasons which make the initiation of physical force an evil, make the retaliatory use of physical force a moral imperative.

If some “pacifist” society renounced the retaliatory use of force, it would be left helplessly at the mercy of the first thug who decided to be immoral. Such a society would achieve the opposite of its intention: instead of abolishing evil, it would encourage and reward it."

Ayn Rand

Video Source: http://www.youtube.com/watch?v=ubC1pOvxSH4&;feature=plcp