Evolutionary explanation of morality self-refuting?

[Tempus]

But anyway, one of the things that is keeping me from leaving theism or at least Christianity is an issue of morality.

Do you believe in Christianity? Do you believe in any god? If you don't then I'd suggest sticking with those concepts simply because you don't like the alternative (a lack of 'objective' morality) is a poor reason. Besides, let's say god(s) exist - how does that make the morality sanctioned by them objective? Because they created us? Because they're powerful enough to enforce it? Ultimately I've found that 'objective' morality tends to break down when you think about it too hard.

A typical notion I read is that morality is simply tendencies in humans caused by evolutionary processes. But W.L. Craig (and probably others) say this is self-refuting:

I'm not usually so dismissive like this, but seriously - do yourself a favour and don't waste time with W.L. Craig.

Given the truth of naturalism, all our beliefs, not just our moral beliefs, are the result of evolution and social conditioning. Thus, the evolutionary account leads to skepticism about knowledge in general. But this is self-defeating because then we should be skeptical of the evolutionary account itself, since it, too, is the product of evolution and social conditioning! The objection therefore undermines itself (On Guard, 2010, p. 144).

I'm sure this argument has been dealt with elsewhere but I haven't been able to find any refutations as of yet.

I doubt it's been dealt with because it makes no sense. It's an observable phenomenon that human psychology is/can be greatly affected by conditioning social and otherwise. But let's pretend this argument (which as far as I'm concerned isn't even an argument at all) is vaild. Let's change the terminology around:

Given the truth of Christianity, all our beliefs, not just our moral beliefs, are the result of God. Thus, the Christian account leads to skepticism about knowledge in general. But this is self-defeating because then we should be skeptical of the Christian account itself, since it, too, is the product of God! The objection therefore undermines itself.

As you can see the argument cuts both ways.