When you say that you are the moral person, and everyone that disagrees with your viewpoint in immoral, the morality you view is a personal viewpoint, most likely caused by religion, parental upbringing, TV viewing, schooling, community attitudes, etc. Your view of morality is yours alone. You have no right to make statements that other are immoral, since morality is a product of all of the items previously mentioned.
You say that killing is bad and is part of our countries moral code, based on the commandments. They gave us the right to bear guns. They murdered all the Native Americans. They wrote that there would be separation of church and state. The list goes on and on in the killing department. I don't think the commandments played any part in how this government was conceived.
You have your religion, which is one of thousands and thousands of religions being practiced today. Your religious truths are personal to you, they have nothing to do with the other billion people believing other ideals. Other religions, many different views of morals. Perhaps you see a vast population of the world is immoral? That must give you a smug, powerful feeling.
What you say is accurate, that morality is a guide to what we say and how we think, however, there are many people in this country, and the world that would argue what you say, and how you think. There are a number of posters on this forum that would do the same.
You bring up killing as immoral. If this was immoral, then that means war is immoral, and all the people in the war that kills another is immoral. If a person was ordered by another person to kill someone, who is immoral? Are both parties immoral? Is it immoral to kill someone out of self defense? Is it immoral to kill someone who is attacking a member of your family? As you can see, Morality is very fragile.
If you were to go to a distant tribe, and this tribe's moral system entailed sacrificing a virgin once a year, or any number of other things that you thought were immoral, however this tribe does not view this as immoral. Actually, to them, this is the height of virtue. You would not be able to argue your morality with them, as your ethics are personal to you, and their view of morality is personal to them. However, you would be hard pressed to call them immoral, because that would not be logical.
You cannot have an absolute standard of truth, that would be impossible. Christians have their truths, Buddhists have theirs, Scientologists have theirs, Atheists have theirs, Satanists have theirs, Muslims have theirs. You are just a small, insignificant viewpoint, in the world of thought on what constitutes morality, virtue and justice.