Reasoning is a human faculty. Therefore, there are reasons only for the actions of humans. For instance, there is no reason for humans. Throw your own bunny. Intelligence is a four-syllable word that has nothing to do with Sex, Drugs or RocknRoll.
Morals serve a purpose.
They are safeguards which lie between instinct and reasoning, and as such, are causal. But neglecting the effect does not negate the relevance of such a morality. Religion, in fact, is the ultimate in moral systemics. Now, its morality infringes on our freedom to explore these issues ourselves. Some morals are too restrictive.