As someone who has spent a lot of time with religious conservatives, I've heard the sort of argument given by Robertson many times before. And they use it as an actual argument used against nihilism, which they tend to think follows directly from atheism. So Scott is completely right to address it as such.

I think Robertson conflates the two because he (and others like him) can't really imagine a coherent non-arbitrary atheist moral realist theory. Can anyone here give a good example of one that couldn't include what the murderer he depicts seems to believe?