I catch your meaning now. When you said "abortion is legal murder," I thought you were saying abortion was already murder by legal definition (but not commonly recognized as such), and that you were preparing to offer some argument that SCOTUS was wrong from a legal standpoint.
If you'd instead said, "Abortion is legalized murder," I would have caught your meaning the first time. Which is essentially an opinion-based critique of the fact that abortion is legal.
So, you do in fact agree that SCOTUS determines what is legal. Okay.
As for legal vs. moral, you're certainly allowed to have your own opinions on what is moral, despite what the laws say. As am I. Example: I don't think all of our gun laws are moral, necessarily. I recognize that places me on the opposite side of some American laws as they currently exist on the books, but places me in line with laws of other countries that practice more vigorous gun control.
I'd echo Strangelove's challenge to you: If "morality is, in fact, absolute," surely someone has written it down somewhere by now?