The atheist position is:" 1. “My moral experience is completely separate from the question of God’s existence, therefore I can be good without God”.
2. “Anyone who only does good, because he believes in God, isn’t really good”
To 1: The argument in honest form is: “What I perceive(!) to be a “moral” experience is completely separate from the question of God’s existence” and this is true. Is the human moral experience corruptable, is it unchangeable, is it universally constant between humans? If the human moral experience is not constant, then it is a variable (changing over time, over place, over emotional state, over genetics, over need). If it is a variable, then there’s no way to weigh one person’s “morality” against another person’s. By what measure except by a changing benchmark would it be weighed? It is like measuring length with a randomly shrinking and expanding yardstick.
→ The depressing conclusion is that humans indeed have moral experiences, but they are not particularly trustworthy, especially when fleshly desires, emotional trauma, material needs corrupt them. This is why no atheist will have an excuse on judgement day: Their conscience testifies of God, their corruptability testifies of their need for a savior, yet they are not looking. Why? Because they worship their corrupt “experiences” tainted by pride (1), comfort (2) and lust (3). This makes them blind to the humility/simplicity (1), repentance (2) and self-denial (3) of perfect, sinless Jesus Christ, our Lord.
To 2: The argument in honest form is an affirmation: “I am good, because I do not act against moral experiences”. It is not hard to be “good” when any experience they have is by default a “moral experience” and, hence “good”. They deny that there’s never any conflict of interest:
When your “moral experience” demands you be charitable to a stranger,
but your stomach demands you spend the money on food, …
and your ambition demands you spend it to further your business, …
and your pride whispers “do not commune with outcasts” or “he is guilty of his own wretchedness”, …
and your lust demands you should focus on etertainment and sex instead, …
and your comfort whispers “he will be fine without me” or “someone else will do it”.
All of these are masquerading as “good” experiences. In their boastful claim: “I can reliably untangle the desires of the flesh from the moral experience” they invalidate their own claim by pridefully elevating themselves above all of past humanity which proves with its wars, destruction, persecution, corruption, crime, starvation and pestilence that this is not the case.
The exact same line of reasoning applies to “human reasoning” itself. It is also not infallible, not uncorruptible, not unchanging and tainted by the same conflicts of interest.