I've seen various responses from people here regarding premise (2) which I will take the time to address broadly.
To deny that there are some acts which are morally reprehensible and inexcusable independently of what individual's opinions of them might be, is itself inexcusable.
In the absence of some defeater, we are justified in trusting our perceptions that there is in fact an apprehendable realm of objective morality in the same way that we trust our perceptions regarding the objective reality of the physical world around us. Can we be absolutely certain of these realities. No. It is logically possible that we are all brains in a vat, or bodies lying in the Matrix. Likewise, it is logically possible that there are no objective moral values, that they are simply illusory. However, seeing as how there is very little in experience that we know with complete certainty, if anything, we do not need to be certain beyond all doubt that there actually exists a realm of objective morality, but simply need to be sure beyond a reasonable doubt, and our moral experiences validates the assertion that there are objective moral values.
Now, there are two ways one might want to object by using the view that objective moral values and duties are illusions built in us by socio-biological evolution. They are as follows:
1. As a defeater for the truth of (2)
or
2. As a defeater for the warrant of believing (2)
With regards to 1., such an objection is an example of commiting the genetic fallacy because the proponent of 1. maintains that there are no objective morals or duties because they originated as by-products of socio-biological evolution.
With regards to 2., the proponent is begging the question on one hand and ultimately is in a self-defeating position on the other. If there is no God, then it is plausibly true that moral experience is illusory. But why think naturalism is true? Naturalists themselves must maintain that God could possibly exist. Therefore, in the absence of a proof on naturalism, the warrant from our moral experiences reinforces (2).
The objection is also self-defeating in that it fails to take into account that on naturalism, all of our beliefs have been selected for their value with relation to survival, not some abstract concept such as truth. Therefore all of our beliefs, not just moral ones, are unwarranted. But if all of our beliefs are unwarranted on naturalism, then the belief in naturalism and the socio-biological explanation of moral beliefs are unwarranted. The objection defeats its own warrant and because of this it cannot be rationally affirmed and in turn cannot defeat the warrant of (2).
In summation, when people like Skavau say that torture is wrong independently of what people think, they are justified in their position. When Michael Ruse himself a defender of Darwinism states: "The man who says it is morally acceptable to rape little children is just as mistaken as the man who says 2+2=5", he is making the comparison of an objective mathematical truth with an objective moral judgment. 2+2 is 4 in Paris, as well as in Pyongyang. 2+2 is 4 even if people say it is 6 or 5 or 3 or 2. Likewise, raping children is wrong whether you're in Paris or Pyongyang and it is wrong whether people think it is or not.