Cardinal Ratzinger on capital punishment and just war

"Not all moral issues have the same moral weight as abortion and euthanasia. For example, if a Catholic were to be at odds with the Holy Father on the application of capital punishment or on the decision to wage war, he would not for that reason be considered unworthy to present himself to receive Holy Communion. While the Church exhorts civil authorities to seek peace, not war, and to exercise discretion and mercy in imposing punishment on criminals, it may still be permissible to take up arms to repel an aggressor or to have recourse to capital punishment. There may be a legitimate diversity of opinion even among Catholics about waging war and applying the death penalty, but not however with regard to abortion and euthanasia."

(Worthiness to Receive Holy Communion, General Principles - sent by Cardinal Ratzinger to Cardinal McCarrick, Archbishop of Washington, D.C., and made public in July, 2004, n. 3)

Benedict XVI on Peace

"The effectiveness of commitment to peace depends on the concept that the world has of human life. If we want peace, we must defend life. This logic not only disqualifies war and terrorist acts but also any attempt on the life of the human being, a creature loved by God. The indifference or denial of what constitutes the true nature of man does not respect this grammar is the natural law inscribed on the human heart.

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The task of education is to guide the maturation of the ability to make choices free and fair, that may go against prevailing opinions, fashions, political and religious ideologies. This is the price of the development of a culture of peace. Obviously, we must banish verbal or physical violence. This is always an attack on human dignity, both culprit and victim."

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Believers today have an essential role of witness to the peace that comes from God and is a gift that is given to all the personal, family, social, political and economic life. You can not allow that evil to triumph by the passivity of good men. It would be worse to do nothing."

Benedict XVI, meeting with political leaders and civilians, Lebanon, 15 September 2012.