It is not that I view secular morality to be superior to morality based on religion, rather I deny that there can truly be any morality in the religious dictates that usurp man's intuitive and evolutionary ethical calculus. Putative religious morality prides itself in its full forfeiture of the moral computation derived from well-being; any behavior is not analyzed for its benefit or damage, rather it must be accepted or rejected in an arbitrary mandate from on high without further consideration.
When religious thinkers try to accommodate this contradiction by saying that even divine demands can change based according to changing benefit, they must rely on their intuitive moral senses which they deny existence. If they truly lacked this sense of internal and human morality, no believer would ever quiver in the least at the blatant immoralities expounded in their dogma.
No Christian or Jew would feel any compulsion to minimize, downplay or morally justify the continuing, explicit and unequivocal demands of God for the Jewish people to commit genocide upon the natives of Canaan in the narratives of Judges and Joshua. Neither would any devout Muslim be remotely ashamed of unabrogated passages in the Qur'an demanding an active bloodlust toward the kuffar or its ubiquitous desire for the most liberal capital punishment.
If it were true that religion were the source of their moral values, religious people would feel unpressed and unbothered by the blood and ire demanded by their gods as they would have not moral sentiments aside from what had been revealed to them in religion.
But we know that religious people do have moral value systems apart from their religions precisely because they do flinch at the ancient morality of tribal society. If it were true that a religion is the sole source of morality, a religious person would be confused if someone else questioned the morality of child-stoning, witch-killing or any other dictate of the Bible. "It's in the Bible," he would say unemotively, "that's the definition of morality."
If the religious truly thought that morality were a mandate and creation of God, they would feel moral indignation only when exposed to violations of His word, but strangely enough, some religious commentators eventually did garner a utilitarian morality by which slavery, some kinds of discrimination and the subordination of women did indeed seed in revolting them as they would any thinking and emotive person.
The extant problem of religious morality is its inherent ossified nature. It, like religion itself, has continued with loyal adherents far past its theoretical usefulness and proper context. Because of this, the religious are concerned with on the most archaic of moral questions dealing with modern issues only with the vocabulary and analyzing capabilities of the desert societies which first invented the faiths. Moral behaviors are indeed changing, being functions of changing economic and social relations. What was beneficial, good personal behavior now is not the same as it was centuries earlier. We must always reevaluate whether the same practices are equally beneficial to our society. Recalcitrant religion disallows this.
Carl Sagan was the one who said that no matter how beautiful a factual delusion or mandate may be, it is always more emotive, fulfilling and constructive to know reality itself, which always manages to be the most sublimely gorgeous and transcendent. Similarly I say that it is the height of morality and utility not to accept arbitrary moral delusions or mandates, but to realize the true nature or morality, that being the behaviors that are tangibly beneficial to the individual, his society and his world. Any moral short-cuts and generalizations proposed by religion inherently force the believer to bypass the utilitarian calculus and force him to act as if he were limited to the tribalism and irrationality native to the context of origin of the religion in question.
A mature person must notice that human morality is not just a result of the sociology and biology of humans, but that evolutionary incentives are the sole source of creating and attritioning innate moral behaviors. Humans are born with moral dispositions because they have evolved in groups that reinforce each other in a way that leads individuals to often deny their personal benefits in favor of their group-members.
Individuals have even developed a way of personally appreciating and socially incentivizing social behaviors. They feel an adulation and pride in giving to and supporting others; it's strange to look at it like this, but it'd be hard to imagine charity existing at all if people felt shame, guilt and regret in performing charitable actions. But humans, having been tempered by billennia of evolution in social groups do indeed feel personally gratified in performing those self-sacrificing actions that all humans innately consider moral.