Here's some random thoughts I had the other day on why I hate utilitarianism, and why I think religion is important for morality.
One of the common arguments I hear (and one I used to parrot myself) is to do with choice. The conjecture is that if religion is considered to be necessary for morality, then you are a bad person. Example: Fedora claims he doesn't murder because he knows it's bad, but Christians only refrain from murder because they believe they will be punished for it.
I couldn't figure out a good way to describe what's wrong with this argument, aside from calling it hyperbole, until I read something by Julius Evola (I forget which book, sorry. I think it's probably Ride the Tiger or Revolt Against the Modern World though).
The basic principle is this:
Morality ranges from the obvious 'truths' we know as people, to certain ideas which are also for the greater good, but don't have an obvious logical reasoning.
When criticized under a utilitarian framework, most values cannot hold up, since we are incapable of comprehending the far-reaching consequences of our seemingly innocuous actions. To give an example of a value which has been argued away would not be useful as an argument, since you've probably already made up your mind that it is not a useful value, so I will instead use adultery as an example.
Most people understand that adultery is bad, but it's not that simple. Having talked to some of my more outgoing friends, it is evident that many people manage to justify certain instances of it to themselves, even when they concede that it's at least bad most of the time. "I was drunk", "he was out of town for a month", "she doesn't put out enough". etc.
When religion dictates that adultery is wrong, there is no question. It's wrong because it's wrong. But when you permit yourself to reason about it, if you really want to, you will find an excuse to break it, especially if you're smart.