Pius XII on brotherhood of mankind

And first of all let us imitate the breadth of His love. For the Church, the Bride of Christ, is one; and yet so vast is the love of the divine Spouse that it embraces in His Bride the whole human race without exception. Our Savior shed His Blood precisely in order that He might reconcile men to God through the Cross, and might constrain them to unite in one body, however widely they may differ in nationality and race. True love of the Church, therefore, requires not only that we should be mutually solicitous one for another as members and sharing in their suffering but likewise that we should recognize in other men, although they are not yet joined to us in the body of the Church, our brothers in Christ according to the flesh, called, together with us, to the same eternal salvation. It is true, unfortunately, especially today, that there are are some who extol enmity, hatred and spite as if they enhanced the dignity and the worth of man. Let us, however, while we look with sorrow on the disastrous consequences of this teaching, follow our peaceful King who taught us to love not only those who are of a different nation or race, but even our enemies. While Our heart overflows with the sweetness of the teaching of the Apostle of the Gentiles, We extol with him the length, and the breadth, and the height, and the depth of the charity of Christ, which neither diversity of race or customs can diminish, nor trackless wastes of the ocean weaken, nor wars, whether just or unjust, destroy.

Mystici Corporis Christi, para 96