I have heard a number of times from apologists like C.S. Lewis, Ravi Zacharias, Donald Keller, and those who subscribe to those authors’ works that the existence of real, god-given principles is proven by our reaction to their being violated. At the same time, they decry people making choices based on their feelings -- this they call relativism.
The aforementioned apologists are correct in that there are some principles at work. I doubt very much that deity hammered them out in its cosmic workshop and then built a world out of them, but I think they’re there. For instance, I’m very much opposed to the idea of being murdered or physically assaulted. I object strongly to the idea of my food being stolen. Am I to believe that these feelings -- and that is what they are -- are the result of my witnessing Thou Shalt Not Kill and Thou Shalt Not Steal being violated, rather than that they are my very natural, wholly biological, response to my well-being being violated? When my dog growls at someone who attempts to take his food away, is he observing religious principle or simply responding to this attack on his well-being? The same goes for an angry bear who has been shot by a hunter’s rifle.
I believe in natural morality, in not doing to others that which I would not have done to myself. That I can plan my behavior accordingly is an example of emotions being tempered by reason: I am making myself stronger, better prepared to live among my fellow creatures. Everyone, to an extent, follows this principle. Rage or power might change the extent to which they follow the “golden rule”, but they follow it all the same. The exceptions are sociopaths. Thus, just because morality may be based on emotional responses is no reason to discredit it.
At the same time, however, feelings themselves must be examined. In the case above, the feelings exist naturally: I don’t want to be hurt, you don’t want to be hurt. In many other cases, however, the feelings exist only because they have been made to be there: the people involved have been conditioned to feel a certain way. In the sect I grew in, women were expected to keep their hair uncut and their rears in dresses -- trousers were “men’s clothing”, and were not to be worn by females. The observance of these "Holiness" and "Separation" standards were very important to the Pentecostal identity, and observance of the rules resulted in smug or honest satisfaction that "God's will" was being observed. Thus, when my pastor’s eldest daughter showed to church with nicely-trimmed hair and a pair of fashionable slacks, her friends were reduced to tears. "Her glory is gone", they said. A Muslim may be driven into a dreadful rage at the idea of Islam being mocked, because for him Islam is world-definingly important and utterly personal. These are both examples of conditioned responses: the feelings are artificial, subjective to cultural background.
These two categories are not wholly mutually exclusive: take the case of a high-school teenager who is reduced to weeping when his team loses a homecoming game. This may have both biological and cultural elements: emotional investment in tribes and groups being biological and that instinct being applied toward an athletics team being cultural. The same is true, too, for xeno- and homophobia. The root may be fear of those who are different, but these feelings are interpreted and magnified by culture.
I do not consider fabricated or culturally-driven feelings to be of much use in my own life, and I doubt laws based on them will be either rational nor humane. To be of use to human beings, moral laws must be based on our natural feelings as they are tempered by reason.