[The] niceties [of Kant about the basis of morality] are doubtless admirably adapted for the lecture-room … They can never be the cause of the impulse to act justly and to do good, which is found in every man ; as also they are powerless to counterbalance the deep-seated tendency to injustice and hardness of heart.
(…) How can that which affects another for good or bad become my immediate motive, and actually sometimes assume such importance that it more or less supplants my own interests, which are, as a rule, the single source of the incentives that appeal to me? (…) It is, what we see every day, the phenomenon of Compassion [Mitleid]; in other words, the direct participation, independent of all ulterior considerations, in the sufferings of another, leading to sympathetic assistance in the effort to prevent or remove them; whereon in the last resort all satisfaction and all well-being and happiness depend. It is this Compassion alone which is the real basis of all voluntary justice and all genuine loving-kindness. Only so far as an action springs therefrom, has it moral value.
Arthur Schopenhauer, On The Basis of Morality – Part III, Chapter V.
Now it is plain to me, first of all, that in this theory the source of the concept ‘good’ has been sought and established in the wrong place. (…) It was ‘the good’ themselves, that is to say, the noble, powerful, high-stationed and high-minded, who felt and established themselves and their actions as good, that is, of the first rank, in contradistinction to all the low, low-minded, common and plebeian. It was out of this pathos of distance that they first seized the right to create values and to coin names for values: what had they to do with utility! (…) The pathos of nobility and distance, as aforesaid, the protracted and domineering fundamental total feeling on the part of a higher ruling order in relation to a lower order to a ‘below’ – that is the origin of the antithesis ‘good’ and ‘bad’. (…) It follows from this origin that the word ‘good’ was definitely not linked from the first and by necessity to ‘unegoistic’ actions, as the superstition of these genealogists of morality would have it. Rather it was only when aristocratic value judgments declined that the whole antithesis ‘egoistic’ ‘unegoistic’ obtruded itself more and more on the human conscience -it is, to speak in my own language, the herd instinct that through this antithesis at last gets its word (and its words) in.
(…) That lambs dislike great birds of prey does not seem strange: only it gives no ground for reproaching these birds of prey for bearing off little lambs. (…) To demand of strength that it should not express itself as strength, that it should not be a desire to overcome, a desire to throw down, a desire to become master, a thirst for enemies and resistances and triumphs, is just as absurd as to demand of weakness that it should express itself as strength. (…) When the oppressed, downtrodden, outraged exhort one another with the vengeful cunning of impotence: ‘let us be different from the evil, namely good! And he is good who does not outrage, who harms nobody, who does not attack, who does not requite, who leaves revenge to God, who keeps himself hidden as we do, who avoids evil and desires little from life, like us, the patient, humble, and just’ – this, listened to calmly and without previous bias, really amounts to no more than: ‘we weak ones are, after all, weak; it would be good if we did nothing for which we are not strong enough.’
Friedrich Nietzsche, On the Genealogy of Morals, First Essay.