If one believes in a designer, then the designer either intentionally or unintentionally was the prime mover in the materials which led to mans moral faculties. In that sense then would God be "Necessary for Morality".
Does this mean that any designer would necessarily have the same morals as the designee?
In fact I would argue against that likelihood for a number of reasons and especially so in the case before us.
First, if the designer did possess the same morals, then the designer would need be incompetent insofar as the situation of a normal human with his or her conscience would not have designed a world in which the nature and scope of evil which prevails would even have been a possibility.
Secondly, when we examine carefully all that we see, we see that the design is that of a life-death, pleasure-pain cycle with no apparent permanence of any sort, no matter that we wish for more pleasure and less pain and eternal permanence of consciousness and growth rather than oblivion.
As regards the supposed "superiority" of God's morals to that of man's, we can easily reply that we would need be presented with an argument which would encompass and not supplant the morals of man.
In other words, if we were to view morality as a Venn diagramm we would see that mans morality was wholly encompassed by the universal set of God's morality. This would indicate that there was harmony, not disjunction.
At present we see only disjunction and it is up to the apologists to concoct an explanation which would make for harmony.
If there IS no harmony and mans morality is entirely disjunctive with regard to God's, then there can be no way to reconcile the two and only an immoral man would accept God's morality.
We would rightly condemn such a man.