Responding to Martin Downes, who asks, "how do you define immorality at all? What is the standard?"
The presumption is in the belief that morality can be defined by something as simple as a standard, when it is in fact complex and difficult to describe succinctly.
For example, principles such as Kant's "treat people as ends in themselves" and his categorical imperative, or Mill's principle of utility, each play a role in morality and interact in complex and not always predictable ways.
None of them stands alone as a principle, and a system of morality based on only one such principle would, sooner or later, result in a perversion of morality in the name of the principle. Thus it is with all standard-base or principle-based moralities.
Morality is a complex weaving or tapestry formed from a variety of principles founded on various perspectives and understanding of people, their environment, and their beliefs.
The actual description of a morality may or may not involve a reference to God, but given an environment with numerous conflicting religions, not to mention the irreligious, a description of a morality founded on a particular theism is impractical and incomplete.
The nature of morality requires us to go beyond religion, requires us to see ourselves not as a privileged seat of moral understanding but as one player in a multifaceted chorus that, together, describes an interwoven, comprehensive, and in some senses infeffable morality.
The idea that religion provides some sort of dispensation from participation in this broader dialogue is what leads people to a narrower, self-justified sense of morality, one in which their personal understanding, to them, outweighs consideration of the broader ethos.
If we take seriously the precept that people matter in themselves, that their happiness is a matter of moral import, that spirituality and devotion are things that can happen in people other than ourselves, then it is necessary to think of morality as broader than religion, and therefore, not to be founded in religion.