The scriptural God is unworthy of worship
If God exists as described in holy books, he is unworthy of worship. He orders and carries out various atrocities.  He also botched the design of the universe. He fails to intervene in disasters, deliberately causes them and orders atrocities to be committed. He ordered Abraham to kill his son as a loyalty test (God relented at the last moment). He has Jephthah sacrifice his daughter as a burnt offering. Genesis 22:1-24 Most humans have an innate sense of morality. However, God fails to meet that standard and is either amoral or immoral. Such a God is unworthy of worship.
Rather than giving open or tacit support to God's crimes, we might try to find something better to do with our time. In contrast, most theists believe that God should be worshipped.
"Because the God who created this universe, if it was created by God, is quite clearly a maniac, utter maniac. Totally selfish. We have to spend our life on our knees thanking him?! What kind of god would do that?"
- — Stephen Fry 
- "Would you worship someone who was going to burn your child to death?"
"And so I accept God and am glad to, [...] Yet would you believe it, in the final result I don't accept this world of God's, and, although I know it exists, I don't accept it at all. It's not that I don't accept God, you must understand, it's the world created by Him I don't and cannot accept. Let me make it plain. I believe like a child that suffering will be healed and made up for, that all the humiliating absurdity of human contradictions will vanish like a pitiful mirage, like the despicable fabrication of the impotent and infinitely small Euclidian mind of man, that in the world's finale, at the moment of eternal harmony, something so precious will come to pass that it will suffice for all hearts, for the comforting of all resentments, for the atonement of all the crimes of humanity, of all the blood they've shed; that it will make it not only possible to forgive but to justify all that has happened with men—but though all that may come to pass, I don't accept it. I won't accept it.[...] If all must suffer to pay for the eternal harmony, what have children to do with it, tell me, please? [...] Besides, too high a price is asked for harmony; it's beyond our means to pay so much to enter on it. And so I hasten to give back my entrance ticket, and if I am an honest man I am bound to give it back as soon as possible. And that I am doing. It's not God that I don't accept, Alyosha, only I most respectfully return Him the ticket."
- — Ivan in The Brothers Karamazov
- God approves of slavery in Judaism, Christianity and Islam.
- According to Christianity, God supposedly places those in authority in power Romans 13:1 , including corrupt and psychotic leaders.
- God commanded atrocities in the Old Testament.
- Jesus allowed a herd of pigs to drown for no reason.
- "The God of the Old Testament has got to be the most unpleasant character in all fiction: jealous, and proud of it, petty, vindictive, unjust, unforgiving, racist."
- "Too much miscarried with [God], this potter who had not learned thoroughly! That he took revenge on his pots and creations, however, because they turned out badly—that was a sin against GOOD TASTE."
Israel suffers several military defeats in the Old Testament, along with various other persecutions. This is interpreted by the Bible as punishment from God for the people not being faithful. Deuteronomy 28:15,25,49 Therefore these types of punishments are considered moral by God.
Gratitude to our creator
Believers credit God for creating us and this is significant grounds for adoration God. However, since God is supposedly infinitely powerful, it hardly took much effort of God's part to create the universe. Also, it does not automatically follow that because God created everything that he should be worshipped (because of the Is–ought problem).
God is king
God has proclaimed himself as king over all creation. However, we cannot conclude from this descriptive statement "God is king", to directly conclude that "we should worship God", which is a descriptive statement because of the Is–ought problem. There is no obligation in human ethics to obey a corrupt dictator, so the same might be said for obeying an evil God.
God moves in a mysterious way
- Main Article: God can't be defined
Believers claim that the ways of God are different to humans and beyond human comprehension. This is an example of Loki's wager in that it unreasonably refuses to discuss something because it is poorly understood. Also, such a God is hardly a role model since he is unknowable. Also, if said deity is fully alien to / beyond human comprehension, why should humans consider God as "good" and "worthy of praise" by their flawed non-divine standards?
Threat of Hell
- Main Article: Pascal's wager
Followers may try to worship God as insurance against going to hell. However, God might perceive this is being done, since it might be faith, not works, that saves people from hell. "Worship is first and foremost a verb, an action".  If you believe God is evil but worship him anyway, that might be insufficient to appease him.
"Buddha says: 'Do not flatter your benefactor!'. Let one repeat this saying in a Christian church : it immediately purifies the air of everything Christian."