Great question!
Say we acknowledge for the sake of argument that a malicious Creator/Designer exists. Seeing as this being is evil, that signifies he does not carry out his moral responsibilities. But then exactly where do those come from? Just how can this evil god receive obligations to execute which he is violating? Who prohibits him to do the immoral things that he does?
Without hesitation, we discover that such an evil being simply cannot be supreme: there needs to be a being that is even higher than this evil god which is the source of the moral duties which he prefers to shirk, a being that is unqualified goodness Himself. Hence, if god is evil well then there must necessarily exist a maximally splendid, incomparable God that is all powerful, all good as well as all loving; One who is actually the very paradigm of good.
Which means that we don’t shower Him with affection for performing His duty. Really He is to be adored for His moral identity as He is fundamentally loving, just, kind, truthful and so on. It is simply because God is that way that all these traits count as virtues to start with.
In effect, God Almighty is good the very same way rain is wet, diamond gemstones are hard, photons tear across space at luminous speeds or cerulean suns blaze. Therefore if we envision God’s goodness in terms of His
possessing definite virtues as opposed to fulfilling selected duties, we get an infinitely more exalted and correct notion of God.
Accordingly, anything and everything standing in opposition to his character must be evil. This is meaningful because "Jehovah hates . . . a lying tongue" which means perforce that lying is evil. (Proverbs 6:16, 17)