Full Idea
Rachels argues 1) If any being is God, he must be a fitting object of worship, 2) No being could be a fitting object of worship, since worship requires the abandonment of one's role as an autonomous moral agent, so 3) There cannot be a being who is God.
Gist of Idea
God must be fit for worship, but worship abandons morally autonomy, but there is no God
Source
report of James Rachels (God and Human Attributes [1971], 7 p.334) by Brian Davies - Introduction to the Philosophy of Religion 9 'd morality'
Book Reference
Davies,Brian: 'An Introduction to the Philosophy of Religion' [OUP 1993], p.173
A Reaction
Presumably Lionel Messi can be a fitting object of worship without being God. Since the problem is with being worshipful, rather than with being God, should I infer that Messi doesn't exist?