So I've been around long enough to see how these moral authority arguments tend to play out. Which has led me to wonder what the point of such arguments are.
But something I do observe tends to be a kind of fear. For example, the fear that without an objective moral standard (e.g. God's Law) people will modify their morality and, potentially, become dangerous. On the flip side, the argument goes, there is a kind of fear that the one who relies only on an objective moral standard is only sharing int he pretense of morality.
Examples:
The Christian says that an atheist has no objective moral standard, and therefore there is nothing to stop them from engaging in horrible behavior and thus are a threat to the well-being of society.
The atheist, then, responds, that if the Christian is only subscribing to certain moral positions because God says so, but does not truly regard such things abhorrent because they are abhorrent, then what stops them from engaging in horrible behavior and thus are a threat to the well-being of society.
Now, obviously I don't think either party (usually) regards the other a genuine threat to the well-being of society. But so goes the broad strokes of the arguments.
Surely, on some level, that there is a common agreement that certain things are abhorrent and endanger the well-being of other human persons and society on the whole and thus we agree on the institution of law to curb evil and promote a common good is, itself, a good thing. The particular pathways we use to come to that position may be varied; and deeper questions can certainly be very interesting.
There seems to be a bigger danger when we start to treat other people as suspicious. When we start othering certain people we entertain dark thoughts that dehumanize our neighbors. And to dehumanize others will consistently produce woes.
-CryptoLutheran