Excerpts from Rav Kook

Love of all creatures requires great effort, that it may be broadened to the fullest extent. Due to our lack of experience, this love may appear to be a matter of little importance, even contrary to the Torah and common ethics. However, [in truth,] it must constantly fill all the chambers of the soul.

The highest level of our love for all creatures must be the love of humanity, which should extend to all its members. Despite the differences of religion and ideology, despite the differences of race and environment, one should try to understand the mentality of the various nations and factions as much as possible, in order to appreciate their character and nature. Then one can know how to base the love of humanity on foundations that lead to actual deed.

Only when the soul is enriched by the love of all creatures and all humanity can the love of [Israel] be elevated to its lofty station and attain greatness, both in spirit and in practice. It is a mean eye that causes one to see only ugliness and impurity in everything beyond the bounds of Israel, the unique nation. This is one of the most awful, debased forms of darkness. It damages the entire edifice of spiritual virtue, the light of which every sensitive soul seeks (Rabbi Avraham Yitzchak Kook, manuscript cited in Mishnato Shel HaRav Kook, pp. 306-307)

~Compassion for Humanity in the Jewish Tradition, 9

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The purpose of Israel has always been to serve as a "vessel that contains blessing" and goodness for all mankind, inasmuch as it was prepared for this from its birth. Therefore, even when [Israel] sins, turning aside from the path of God, it does so only because it has been misled to think that it will actually fulfill its spiritual mission by repudiating the Lord, its God. However, its true motivation is [nevertheless] to be a blessing unto all who are created in the Divine image and to delight in bringing benefit and happiness to all mankind, [a calling] that is permanently fixed in the innermost depths of its soul (Rabbi Avraham Yitzchak Kook, Ein Ayah, Berachos II: 115)

~Compassion for Humanity in the Jewish Tradition, 143