Atheists are immoral
"The fool hath said in his heart, There is no God. They are corrupt, they have done abominable works, there is none that doeth good."
"[Atheists] know perfectly well that if everybody didn't believe in God, the comfortable lives they live, in extremely agreeable suburbs, where they can trust people will not cheat them and rob them and mug them and rape them, could come to an end."
As an argument for belief in God, criticising atheists in this way is an appeal to consequences and begs the question that Christian morality is correct.
Evidence typically cited includes:
- Hitler was an atheist
- The Nazi Party was atheistic
- Stalin was an atheist
- Mao was an atheist
- Pol Pot was an atheist
- 20th century atrocities
- Increased premarital sex
- Increase in divorce
- Increase in pornography
- Weakening of family structure
- Public acceptance of homosexuality
"The logical result of atheism, a result we have seen right in front of our eyes in one of the world’s oldest and proudest nations, is severe moral decay."
- — Sarah Palin 
Atheists have no source of morality
- Main Article: Secular morality
- "Another thing is why in the world would an atheist be moral? I understand there can be moral atheists and I do have a few atheist friends that I'm trying to work on. But why in the world would you be a moral atheist? You see, there is no point in it. If you don't believe in life after death is a thing, then as long as you are not going to jail, there is no point in being a moral atheist."
- "This, therefore, is the fundamental difference between converted Christians and atheists. Christians have a conscience that is continually instructed, nurtured and strengthened by the Scriptures and prayer, atheists do not. "
- "It is also essential to reject as having any hold over us anything or anyone who asserts that a good can be achieved without it being instrumental to the purpose to existence. i.e. without it being for the sake of Allah. "
Atheists do not derive their morality from a religious basis but that does not mean they are not moral whatsoever. It just means that any morality is derived from a source elsewhere. After accusing atheists of having no basis for morality, apologists sometimes make the argument from the meaning of life or the moral argument.
This argument contradicts the idea that atheism causes immorality: since atheism allegedly has no moral basis, it cannot motivate any action either moral or immoral.
Perception vs. reality
It is important to distinguish between the general perception of atheists, which is often negative, and the actual behavior of atheists, which is usually at least as good as theists.
Americans generally have a poor view of atheists. A study of Americans, including theists and atheists, found that they judged various immoral acts to be representative of atheists but not of other social and religious groups. 
- "Atheists, including those who brought us the Enlightenment, have often been a beneficial force in the history of human thought and religion. They have forced societies to examine empty religious platitudes and hollow religious concepts. They have courageously challenged the moral hypocrisy of religious institutions. The humanistic values of the Enlightenment were a response to the abuses by organized religion, including the attempt by religious authorities to stifle intellectual and scientific freedom."
A study found that fictional evil-doers were assumed to be atheist an almost all countries, particularly ones with a higher religiosity.
Moral concern higher among the religious
An interesting study found a correlation between self reported moral concern and self reported religiosity.
- "We find that religious belief is robustly positively associated with moral concern (4 measures), and that at least part of the negative association between belief and analytic thinking (2 measures) can be explained by a negative correlation between moral concern and analytic thinking. [...] It is important to note that individuals with high levels of moral concern will not necessarily behave more ethically in all situations.[...] Moral concern was indexed with the 7-item Empathic Concern subscale of the IRI (). A sample item from the IRI-EC is “I often have tender, concerned feelings for people less fortunate than me” [...] the measures of moral concern were all subjective (either self or peer-report). More objective measures of moral concern are wanted to further establish their relationship to religious and spiritual belief."
Another possibility is that religiosity causes an aggrandised view of a person's own morality. We don't see religious societies being significantly more moral than less religious societies.
The claim that atheists are incapable of any moral actions is absurd in light of evidence to the contrary. In studies that compare overall behavior of different religious groups, atheists often are shown to be more responsible, ethical and law abiding.  Other evidence suggests that morality is very similar between theists of different religions and even non-theists. 
"Which is more dangerous: fanaticism or atheism? Fanaticism is certainly a thousand times more deadly; for atheism inspires no bloody passion whereas fanaticism does; atheism is opposed to crime and fanaticism causes crimes to be committed."
- — Voltaire
Apologists sometimes claim that atheists have a flawed moral system or that morality depends on religion. However, the latter is a separate issue because this does not necessarily imply that atheists are morally worse than believers. For instance, Christians supposedly know not to commit murder but the murder rate is lower in non-religious countries. 
The claim "Christians have their conscience continuously nurtured and structured by the bible, but atheists do not" suffers from flaws, like omitting the existence of all non-Christian theists with vastly differing dogmas (one can just as validly claim that this different religion reinforces morality), and not clarifying how a fundamentalist theist's conscience is not always "growing" with their scriptures' teachings, but is constrained within texts (which often reflect by today's standards narrow-minded and bigoted opinions of ancient tribes) demanding blind obedience and not allowing one to question their validity or morality (forming an evolving conscience with reason and empathy is not the same as doing what a single source orders without giving it a thought).
Theists are also immoral
Theists commit acts that are motived by their religious beliefs. Judging from the Bible, Christians are less moral than atheists based on God commanded atrocities in the Old Testament and the rest of Christian morality. Apologists also have to explain the moral failure of mainstream religion. All throughout the history of most religions, there have been numerous atrocities involving numerous deaths and that includes Christianity e.g. the Inquisition and the Crusades. Christians typically fail to realize this and when encountered with a response such as the above, they will most likely resort to weak rationalization to justify both their belief and their argument.
- the camo christian, why atheism doesen't make sense, 11 Sep 2016
- Chris Hedges, I Don't Believe in Atheists, 2008
- Phil Zuckerman, Atheism, Secularity, and Well-Being: How the Findings of Social Science Counter Negative Stereotypes and Assumptions, Sociology Compass 3/6 (2009): 949–971, 10.1111/j.1751-9020.2009.00247.x