As with all encultured groups, there’s a difference between esoteric and exoteric atheists. The former are existential, visionary, and cultish or countercultural, while the latter are mainstream and propagandistic. Nietzsche was an existential atheist (as am I), while the New Atheists were propagandists. Existential atheists face the big problems of nihilism and absurdity squarely, whereas exoteric atheists defer those problems to the esoteric thinkers since these mainstream folks just want to get on with their day.
This isn’t necessarily hypocritical since no one can address all problems. Labour must be divided and priorities established. Similarly, we don’t all perform scientific experiments to support the models we take for granted. No, we defer to the scientific experts. Not all atheists are philosophical experts. Some atheists have other functions, such as spreading the word or combatting religious fundamentalism.
The question of whether liberalism depends on Christianity is a red herring, when it comes to the threat of nihilism. Certainly, Christianity doesn’t help us decide whether to side with a potentially tyrannical, mad God (all absolute rulers are likely corrupt, according to common political experience) or with the rebel angels. Christian dogma declares what we should do, but that’s not philosophical.
Moreover, Christianity didn’t invent its values, but took them from Judaism and Greco-Roman philosophy, and modern thinkers bypassed the dead end of Christianity and went straight to some of the earlier sources, ancient Greco-Roman naturalism and humanism. Modern philosophy reconstructs humanist values without Christian theology.
The question of nihilism, or of whether life is worth living, is a deep one that could afflict all thinkers, regardless of whether they’re atheists or theists. The notion that God exists, bungled Creation by provoking a war in heaven, lost his treasured humanity, and means to redeem humans by killing his son is plenty absurd, and it’s valid even for Christians to wonder whether they want to be associated with that bizarre rigmarole.
