How should Atheists respond to religious belief?
Atheists should judge a religion or religious belief by the amount of good or bad that it brings about, and not the amount of evidence supporting it: The truth is not that valuable. A lack of evidence, by itself, is not that much of a reason to criticize a religion, but only a means by which religions which are causing harm to individuals or society might be critiqued.
I'm an atheist. I believe that there is probably no God. While there might be some kind of 'first cause' out there, I - personally- have yet to find any evidence for a God (or gods) that are active in the world: that perform miracles, prescribe a moral law, or will send us to an afterlife after we die. By extension, I think that all of the major world religions are probably not true, and that the holy scriptures that many religious people follow probably contain no revelation of God.
What does not follow from this, however, is that I think religious people are probably wasting their time, or that I should probably try to help religious people to understand (what I believe to be) the truth. This includes an implicit assumption about the value of truth - that we should aspire to or value the truth at all costs. However, the truth can come at a price.
I want to start by getting it clear that there is a truth out there. It is either true or false that God exists as he is represented in, for instance, the Bible. It cannot be 'true for you, but not for me'. Simply, the statement 'The Christian God exists' is true or false. Truth is a simple matter of fact that is determined by the way the world is. For instance, either the state of the (meta-physical) world is such that Jesus is the son of God and God revealed himself only through the Bible (making Christianity true and Islam false); or that Jesus was not the son of God, but only a prophet, and that Allah revealed himself, via the Prophet Muhammad, through the Qur'an (making Islam true and Christianity false); or neither Christianity or Islam are true. 'Partial truths' or 'truths from a particular position' simply do not make sense.
While I'm not going to get into the arguments here, I personally don't believe in (and am not aware of any substantial evidence for) the existence of a benevolent, omnipotent and omnipresent God (although, as I mentioned earlier, a case could possibly be made for some kind of a 'first cause'.) I personally think that religious people have faith in something that is 'simply false'. It cannot be 'true for them'. [This might be quite a blunt and antagonistic way of putting it, but at least I don't believe (as the scriptures of the three main monotheistic religions teach) that people who do not share my beliefs deserve to be sent to hell to be tortured on account of their non-belief!]
So, then how should atheists, like me, respond to religious believers - to people whom I think have faith in something that is false? Should atheists try to combat (what they believe to be) falsity in the world; should they allow 'each to their own'; or should they promote religion when it is bringing about good in the world? Two interesting, and polar opposite, responses to this question come from Dawkins and Nietzsche. They differ mainly in the value they place on the truth.
Dawkins (left) seems to place a very high value on the truth. His main attack on religion seems to be simply that it isn't true (although he does also attack religion on other grounds, e.g. for offering a twisted and contradictory set of moral rules.) In the Selfish Gene, Dawkins shows that evolution can explain how we got here, without any need to invoke the idea of a creator (or an 'intelligent designer'.) He has repeatedly asserted that we should not believe in anything we have no evidence for, or does not help in explaining observable phenomena (such as our own existence.) He has claimed that - just as with Bertrand Russell's analogy of a teapot which is orbiting the sun between the Earth and Mars - there is no evidence or reason to believe in God, so we ought not to believe. Dawkins makes the implicit assumption that we ought not to believe what is false or lacks evidence.
According to Nietzsche, then, it is probably false that God exists. However, Nietzsche does not think that we ought not to believe in God. In fact, Nietzsche is deeply troubled by the death of God! The full quote from the Gay Science reads: "God is dead. God remains dead. And we have killed him. How shall we comfort ourselves, the murderers of all murderers?" Nietzsche repeatedly has stressed his concern that a period of 'suicidal nihilism' could follow the death of God - that, upon realising that religion is false, we realise that there is no meaning, purpose or objective value in the world, and become terribly depressed. While, in many ways, Nietzsche deeply hated Christianity - he called those who believed in it 'sick' and 'slaves', he also had a deep respect for it: Christianity gave those who were sick a sense of meaning and hope, and it helped them to positively evaluate their own lives. Nietzsche wrote in the Genealogy of Morality that Christianity "should rule the herd, but not reach out beyond it", i.e. that the 'weak' should believe in Christianity, so long as their values and beliefs do not have a negative impact on the 'strong' (whom Nietzsche considered himself to be.)
While I am in no way trying to consider than religious believers are 'weak' (as Nietzsche did), or that they rely on religion to avoid suicidal nihilism, I do, like Nietzsche, think there can be a positive value in religion irrespective of it's true value, i.e. even if it is false. Religion can be (and often is) a source of good in the world: Religious people will often engage in great acts of charity in the name of religion, for instance, and can turn to God as a source of comfort (e.g. following the loss of a loved one.) Equally, religion can be a source of bad in the world, whether or not God exists: Religion can be used as an excuse for war or terrorism; can lead to sexism or homophobia; and religious tradition and dogma can lead individuals to be close-minded or unquestioning.
Like Nietzsche, then, I am advocating that an atheist's view of religion should be determined by the good or bad that each particular religion or religious view brings about, and not the (lack of) evidence that it has supporting it. Atheists need to realise that religion in some (but by no means all) circumstances can be something that is valuable and good in the world. Non-believers should not mindlessly criticize religion just because they believe it to be false. This can be offensive, and in most circumstances won't have much of an impact in 'converting' religious believers to atheism. Of course, atheists need to ensure that the facts are out there, and need to encourage religious people to look for evidence and question their faith as part of a healthy debate; but this does not mean that they need to explicitly and openly criticize religious believers that are doing 'good' in the world.
Atheists should only openly criticize religion when it is (or they have strong reason to believe it to be) having a negative impact on the lives of it's followers and others. A 'lack of evidence' for God is not really much of a reason for atheists to criticize religion; but should merely be a tool that atheists can use as part of a critique of the religious views that are having a negative impact on our world.