Does morality derive directly from G-d? And does the derivation make a difference? My answer is similar to what the rat-bastard Voltaire is supposed to have said: "If there were no G-d, it would be necessary to invent him."
In "The Case for Judeo-Christian Values: Divine-Based Morality" (1/11/2005, http://www.jewishworldreview.com/), Dennis Prager defends the need for G-d-based morality: "if there is no G-d who says, 'Do not murder,' ... then murder is not wrong. Many people may think it is wrong, but that is their opinion, not objective moral fact. There are no moral 'facts' if there is no G-d; there are only moral opinions."
To Prager, moral fact can only issue from G-d's will; more than this, G-d's will creates the very substance of morality. Man-made morality is not and cannot be true morality: it cannot make an objective, transcendental standard.
But there is another approach to morality worth considering: not only are there are no moral facts without G-d, but there are no moral facts anyway -- at least in this world. G-d's moral will may be "Do not murder," but on Earth our defense after the act is "It doesn't qualify as 'murder.' There's a justification. There's a technicality." In some situations, we can even read G-d's will to favor our moral position.
However, just because morality is subjective doesn't mean we must act as though moral facts don't exist. Just the opposite: we can, should, and need to behave as if worldly morality were objective and concrete. Otherwise, as Prager notes, virtually any act or behavior can be construed as permissible. Anything can be justified or explained away.
The fact is that we need to believe in an objective moral reality. And we need to act accordingly, but we don't do a very good job of it -- not the so-called secular moral relativists, not those who proclaim to subscribe to Judeo-Christian values, not Prager, not me.
I hear and read so much name calling these days: "secularists," "conservatives," "elites." There's no end to the names, and attached to each name is a ready-made moral criticism against it. In these instances, it seems to me that those who claim morality and claim themselves to be moral not only discourage honest debate but also attempt to prevent people from approaching G-d.
For myself, I am prepared to let the necessary illusion of G-d-based morality guide my actions, but it will mean little unless I also jettison the unnecessary illusion of self-based morality.