Doesn’t your religion answer for you? if you submit to the Catholic God, the reason you shouldn’t do X (something God says not to do) which leads to a greater good Y (in your estimation) is precisely because you’ve chosen to do what He tells you to. Atheists (those who do not believe in gods) are free to do whatever they judge to be the best course of action.
I believe you misunderstood Pieman’s question. He’s not asking why God asks us to do things that we believe are against the greater good; personally, I haven’t found any Catholic teaching that I find morally abhorrent. He is asking what the point is of being moral at all if, after all, God’s will is sovereign, so all the evil in the world must be according to His will. I admit it is a rather perplexing problem.
Perhaps it is a sign of just how much God respects the gift of free will that He has given us. If some people (most, rather) prefer evil to God, He will not stop them from reaping what they have sown (i.e. hell). If what is best for those who hate God is separation from
Him, and if God wants what is best for His creation, who are we to say the existence of evil is unfair? True freedom and happiness are the choice of good over evil when given one, rather than mandatory coercion into doing what is right against your will.
But then, perhaps Pieman really is questioning God’s morality. If so, I ask him why he believes his sense of morality is supreme in the first place. That goes for you, as well, LifeIsAbsurd. If you believe that you are little more than an accident of circumstance, how do you know your morality is the true morality? Personally, I have the humility to realize that I cannot possibly decide what is good and evil for myself. I believe there is an objective moral standard, and it seems much more likely that a creator would reveal it to his creation, as God does, than the possibility that we have to discover that standard for ourselves, just as we discover scientific mysteries. Human intuition and common sense tell us that morality is different from physics and mathematics. Why? Because the laws of morality can be broken (ironically, by us, while physical and mathematical laws could only be broken by God, if at all; yet moral laws can’t seem to be broken by God…).