Good is a lie. Good is evil. Nietzsche explored morality a lot in many different books, but it comes to a head in Ecce Homo. He talks about how our morality is typically based on Christian values (especially in the West). Yet, the people preaching Christianity, aka priests, are liars. The Christian idea of a soul is not true. This idea shames our mortal body to be lesser than.
Christian values promotes that which is unnatural. For example with sex. We view sex and reproduction as something that is immoral and wrong, yet it's in our natural instinct to reproduce and give life. He mentions this before:
The principle runs thus: ‘preaching chastity is a public incitement to perversity. All despising of the sexual life, all besmirching of it by calling it “impure” is the crime of crimes against life - it is the true sin against the holy spirit of life.’ (Ch 3. A. 5)
By shaming sexual expression and intimacy we shame life.
Those that are good are also as Nietzsche calls them “the beginning of the end”. He calls them this because those that are perceived as good judge and push away new thoughts from those that are different. They don’t welcome different opinions because their view is so black and white:
The good - they cannot create: they are always the beginning of the end - they crucify him who writes new values on the tablets, they sacrifice the future to themselves, they crucify all human future! The good - they have always been the beginning of the end...
And whatever harm the world-slanderers may do, the harm done by the good is the most harmful harm. (Ch. 4 A. 4)
He claims how our views of good are essentially believing the lie:
The condition of existence of the good is lying - put differently, not wanting at any price to see how reality is constituted, which is not in a manner so as tho challenge benevolent instincts at every turn, still less so as to permit the intrusion of short-sighted, good- natured hands at every turn. (Ch. 4 A. 4)
The lack of vision to see others points of views because of their ‘truths’ are what Nietzsche fights against. He is the first immoralist because he stands against this concept of Christian Morality as "the good and the just would call his overman a devil...".
Those that create good, must then also create and own evil. Thus this morality is both good and evil.
I’ll leave one last thought on this idea. That God and religion is created as to hold us down against our natural will and instinct to survive and pursue that which we want. It's an inhibitor:
Anyone who discovers morality discover at the same time the valuelessness of all the values that are or have been believed in... The concept of ‘God’ invented as a counter-concept to life - bringing together into one dreadful unity everything harmful, poisonous, slanderous, the whole mortal enmity against life! The concept ‘hereafter’, ‘true world’ invented in order to devalue the onlyworld there is - so as to leave no goal, no reason, no task for our earthly reality! The concepts ‘soul’, ‘spirit’, ultimately even ‘immortal soul’ invented so as to despise the body, to make it sick - ‘holy’ - so as to approach with terrible negligence all the things in life that deserve to be taken seriously... The concept ‘sin’ invented along with its accompanying torture instrument, the concept of ‘free will’, so as to confuse the instincts and make mistrust of the instincts into second nature! ... And all this was believed in as morality! (Ch. 4 A. 8)
As we fight against this dated concept of morality, we say: behold the man.