From Mein Kampf:
Nature generally takes certain measures to correct the effect which racial inter-breeding produces. She is not much in favour of the mongrel.
Not only are they deprived of the higher qualities that belonged to the parents who participated in the first crossing, but they also lack definite will-power and vigorous vital energies, owing to the lack of harmony in the quality of their blood.
At all critical moments in which a person of pure racial blood makes correct decisions, that is to say, decisions that are coherent and uniform, the person of mixed blood will become confused and take half-measures.
Hence we see that a person of mixed blood is not only relatively inferior to a person of pure blood, but is also doomed to become extinct more rapidly.
From Mein Kampf:
One can breed a herd of animals, but from a mixture of this kind, men such as have created and founded civilisations would not be produced. The mission of humanity might then be considered at an end.
Those who do not wish that the earth should fall into such a condition must realise that it is the task of the Germanic States in particular to see to it that the process of bastardization is brought to a stop.
Our contemporary generation of weaklings will naturally decry such a policy and whine and complain about it as an encroachment on the most sacred of human rights.
But there is only one right that is sacrosanct and that right is at the same time a most sacred duty, namely, to protect the racial purity so that the best types of human beings may be preserved and thus render possible a more noble development of humanity itself.
A völkisch State ought, in the first place, to raise matrimony above the level of continual racial adulteration. The State should consecrate it as an institution for the procreation of creatures made in the likeness of God Himself and not of monsters that are a mixture of man and ape.
The protest which is put forward in the name of humanity does not befit the mouth of a generation that makes it possible for the most depraved degenerates to propagate their kind, thereby imposing unspeakable suffering on their own products and on their contemporaries, while, on the other hand, contraceptives, are permitted and sold in every drug store and even by street hawkers, so that babies should not be born to the healthiest of our people.
In this present State of ours, whose function it is to be the guardian of law and order, our national bourgeoisie looks upon it as a crime to make procreation impossible for syphilitics and those who suffer from tuberculosis or hereditary diseases, and also for cripples and imbeciles.
But the practical prevention of procreation among millions of our very best people is not considered an evil, nor does it offend against the moral code of this hypocritical class, but rather suits their short-sightedness and mental lethargy, for otherwise they would have to rack their brains to find an answer to the question of how to create conditions for the feeding and maintaining of those yet unborn beings who will be the healthy representatives of our nation and will, in their turn, have to perform the same task for the generation that is to follow them.
How devoid of ideals and how ignoble is the whole contemporary system! No effort is being made to perfect the breed for the future, but things are simply allowed to slide.
The fact that the churches join in condoning this sin against the image of God, even though they continue to emphasise the dignity of that image, is quite in keeping with their present activities.
They talk about the Spirit, but they allow man, as the embodiment of the Spirit, to degenerate to the proletarian level. Then they gape with amazement when they realise how small is the influence of the Christian Faith in their own country and how depraved and ungodly is this riff-raff which is physically degenerate and therefore morally degenerate also. To balance this state of affairs they try to convert the Hottentots, the Zulus and the Kaffirs and to bestow on them the blessings of the Church.
While our European people, God be praised and thanked, are left to become the victims of moral depravity, the pious missionary goes out to Central Africa and establishes mission-stations for Negroes.