[DarkMuse]

You are being absolutely relativistic throughout your entire post.

Morality is completely dependent on personal opinion

No, no it most definitely is not. Morality is absolutely and definitively objective.

murder being morally wrong is only wrong when someone uses their opinion to deem it wrong.

Oh but wait...uhm... isn't your opinion then an opinion of someone elses opinion? so wait, who's right here? Where's the truth? Some classic circular logic.

The answer to your question boils down to this:
What is truth?
Are you saying truth varies depending on the person you ask? One may say murder is wrong, while another may say it is right. The truth is different person to person. But, that doesn't make sense, because then there can be no truth. So, are you saying truth does not exist?

Morality = objective
HIGHLY debatable. No definitive answer one way or the other (objective vs subjective)
However, your observation of the obvious relativistic is quite correct as well as it being circular in terms of the used logic.

I think that if OP honestly attempts to rewrite his argument in a more specific and logically correct manner (I mean that as in logical forms, not in the sense that some would seem to be rude or insulting) he would find that the core of his argument is, for lack of a better word, wrong.

Still was nice to see an attempt at philosophical conversation here; I had no idea even a few people were versed in the art :-)