The con position is self-contradictory because it requires assuming as a matter of moral absolute that going to Heaven is a Virtue and that going to Hell is a Vice. That's not true Divine Command Theory. That's just moral realism (ie morality is universal) plus the threat of the supernatural.
From the beginning itself we have a mere hypothesis of god creating the human beings and the surroundings . "Creation" by itself is understood and termed as "Morally good" , so we end up relating every morally good thing to the god . Even if we go through some popular stories ( or maybe just evolved rumors) , we have always been given a morally good character of the " So called god" by our ancestors , in some ancient writings or maybe the religious books which we tend to follow and hence we conclude every morally good thing to GOD .
Divine Command Theory is a terrible system. Sam Harris tears it apart: "It is psychopathic because this is a total detachment from the, from the well-being of human beings. It, this so easily rationalizes the slaughter of children. Ok, just think about the Muslims at this moment who are blowing themselves up, convinced that they are agents of God’s will. There is absolutely nothing that Dr. Craig can say against their behavior, in moral terms, apart from his own faith-based claim that they’re praying to the wrong God. If they had the right God, what they were doing would be good, on Divine Command theory.”
Divine Command Theory is just an excuse used by people to do terrible things.
The people who claimed to speak for their god, used preexisting moral values when telling others what is moral. For instance, it is natural for all species to look out for their group. The closer the group member, the more important the value. This is not only consistent in most if not all religions but in other animal species. If something was only good because a god said so, then people who did no hear the message would have a different basic morals.
In the Christian bible, many of the commandments (Exodus 20: 12-17) are just stating the obvious to make the source sound more legitimate. By stating a rules that everyone would already agree with, it makes it sound like I am a great ruler. It also implies that the rest of my rules should be looked at as being moral. (Exodus 20: 1-11). By associating rules about faith with rules about life, it makes disbelief look immoral. In fact, because it is placed before the rules of life, it is more immoral to go against the religion than to go against life morals.
As I stated, morals are there to benefit the group(s) we belong to. For those who are not in or oppose our group(s), their value is either nothing or negative. This means the law that applies to our group, either does not or just the opposite law applies. That may have sounded a bit confusing so let me explain by example. "Thou Shalt Not Kill" applies to all in your group(s). Not only should you not cause their death but you should also prevent them from being killed. If a group of people are outside your group. Their lives matter less. Not that you should kill them but you don't need to protect them either. As far as those who oppose your group. People that threaten them, not only should we not protect them but it is acceptable if not necessary to kill them. This is why the bible tells people to kill others. Even when they are in the group yet oppose them. Example: "Honour thy father and thy mother" supports the group (family). Yet, if a child strikes or curses their parents, they should be put to death (Exodus 21: 15&17) because is goes against the group (family) even tho they are members of the family.
Because various cultures differ with groups and their importance, causes their belief to follow that group mentality. Because an outside group lacks importance, things like slavery were acceptable. It was only once we considered people of all lands as deserving of respect that we found slavery to be immoral.
Clearly morals are there to benefit the group and to claim it is commanded by a god is to state that the god just proclaimed something obvious.
That is the question that the Euthyphro Dilemma asks. The Euthyphro Dilemma is a philosophical problem concerned with the view of morality as related to theism (divine command theory). The first horn of the dilemma asserts that God commands the good because it is good, and if that's the case, then moral goodness exists independent of God's commands, in other words morality itself is not based on divine commands. Whereas the divine command theory argues that the good is good because it is commanded by God. If moral goodness depends on divine commands, that would make God's commands arbitrary.
Socrates and Euthyphro discuss the nature of piety in Plato's Euthyphro. Euthyphro proposes that the pious is the same thing as that which is loved by the gods, but Socrates finds a problem with this proposal: the gods may disagree among themselves. Euthyphro then revises his definition, so that piety is only that which is loved by all of the gods unanimously.
At this point the dilemma surfaces. Socrates asks whether the gods love the pious because it is the pious, or whether the pious is pious only because it is loved by the gods. Socrates and Euthyphro both accept the first option: surely the gods love the pious because it is the pious. But this means, Socrates argues, that we are forced to reject the second option: the fact that the gods love something cannot explain why the pious is the pious. Socrates points out that if both options were true, they together would yield a vicious circle, with the gods loving the pious because it is the pious, and the pious being the pious because the gods love it. And this in turn means, Socrates argues, that the pious is not the same as the god-beloved, for what makes the pious the pious is not what makes the god-beloved the god-beloved. After all, what makes the god-beloved the god-beloved is the fact that the gods love it, whereas what makes the pious the pious is something else. Thus Euthyphro's theory does not give us the very nature of the pious, but at most a quality of the pious.
The argument is set up to trap the respondent (probably a believer in God) into what at first glance seems like a lose-lose scenario for the theist. If God wills it because it's good...Then He can't be all powerful since He would be adhering to a standard above His authority. If it's good because God wills it...Then moral good becomes arbitrary. The false assumption smuggled into the Euthyphro Dilemma is assuming one must logically precede the other. God's essence is total perfection and he wills good because he is the perfection of goodness by his very nature. He necessarily must will goodness because non-goodness does not exist in Him.