Socrates was a Greek pagan as were all of the Greek philosophers. Plato had some things right - ideals do exist - problem was the greek gods were not big enough to be the source of the ideals. So, using Greek philosophy as your proof God's moral precepts are arbitrary doesn't work. It may have been arbitrary for the Greek gods, but not the REAL God. The Christian God is much bigger than any of the Greek gods - their gods were limited in their power and authority.
Your problem goes deeper than this, however. If morals are arbitrary, then there is no right and wrong, except that which man states as his personal preference (or societal preference). On this basis, relativism is your only refuge. If relativism is your only refuge, you are in big trouble because moral relativism is logically and practically indefensible. I can e-mail you a sound refutation for moral relativism if you like.
Problem is, there is only one God and one creator (Aristotle's law of contradiction came after Socrates death)so there is no disagreement amongst the gods.
I explained this earlier, it is so easy for you to say that since moral law comes from God, it must be arbitrary. The problem with this is that God is eternal, He is not a man. He created the universe and every single spec and idea in it. The universe conforms to God's personality, in fact, it is held together by natural laws that God invented. God invented love, justice, truth, goodness and holiness. Man can know these things only because man is created in God's image and is given the capacity for them to a certain degree. All goodness, truth, and yes, HOLINESS, flows directly from God Himself. It is part of His character. Don't you like love and goodness and justice? Or is that you don't want to bow a knee to your Creator? He is THE source and THE perfect standard for justice, mercy, goodness, truth, and holiness. The God I speak of spun the billions of glaxies into their orbits. He is a VERY BIG God. Besides Him, there is no other.
He is the infinite reference point that is needed as a standard in order to judge what is good and evil. Without that standard, you cannot judge what is good and evil, you can only have your personal tastes (I like chocoloate, you like vanilla)
Without God, you have no standard. You can say God's laws are arbitrary, but since He made you, He can do that. How can the clay tell the potter what to do? Would you rather have an evil man set the moral standard? Or is that you just do not want to be accountable for your actions in life, hmm? What is wrong with perfect justice, goodness, mercy, truth, and holiness? Can you think of a better standard? From whence would it come? Are there any men who have these attributes?