If the assertion that there is a god is nonsensical, then the atheist's assertion that there is no god is equally nonsensical, since it is only a significant proposition that can be significantly contradicted.
The only possible basis for a sound morality is mutual tolerance and respect: tolerance of one another’s customs and opinions; respect for one another’s rights and feelings; awareness of one another’s needs.
If one takes full account of the persecution of heretics, the frequency and savagery of the religious wars which Christianity had endangered, the harm caused, especially to children, by the pernicious doctrine of original sin, a case could be made for saying that the world would have been better off without Christianity.