What theists dont want to except is the fact that even if you could put a god in the equation and say "yes our morality comes from our god", its STILL subjective. Its subjective to what the whims of the god is.well then you can't argue when someone does something that you don't agree with because he gets to choose HIS own morality. In other words, there is no immorality.
A better way of looking at it is in regards to personal well being. In that aspect we CAN SAY when things are good or bad. Like drinking battery acid is bad, along with letting someone drink battery acid.
The subject of morality isn't an easy one, and when theists pull it out like its a show stopper because they want to shoehorn their god into it like it makes the subject closed is rather laughable.