NYC Trials: Politics or Justice?

I have to admit that this story is getting far more traction than I initially thought that it would get. At first I was really at a loss in understanding why it was getting such outrage from the Republican network. But the more I see the less I like, and I am beginning to see why there seems to be such an outrage. I can certainly also understand why New Yorkers are so against the move made around the trial. What I am failing to understand is how anyone from the left is able to support such a move being made by the administration. I can see no valid arguments being made by those on the left that would justify the Attorney General moving the trial to a civilian court in NY instead of a military tribunal in Cuba. None-the-less, Khalid Sheik Mohammed, along with 4 others will be tried in a civilian court in New York rather than in a military tribunal. And I am not pleased that this is the case.
Exactly Why is this a Good Idea Again?