I think you're confused. There are clearly normative questions; "Should I do X?" for any value of X is a normative question. You might have intended to contend that there are no normative facts: that there is no "right answer", as it were, to normative questions, merely what we choose to do.
However, this is not something that science can prove, at least without adding the claim that the only facts there are are physical facts. You're basically suggesting that we open up people's heads, look around, go "Nope, no norms here!" and take that to be evidence that they don't exist. This is problematic at best, since were they to exist, normative facts would seem to have properties quite at odds with physical facts, and your assertion starts to look question-begging.
Metaethics is not my area, so I'm afraid all of this is rather rough and ready, but the SEP article [1] is a pretty decent starting point.
Yes of course there's the distinction between the normative question and the underlying reality that question is about; my point doesn't require a distinction so I found it useless to make it and just went with the phrasing of the post I was replying to.
My point was that there is nothing science won't be able to prove; and that there is only physical reality, and facts, and that once we crack the 'code' (as in 'security code', not 'programming code', although in another discussion I'd posit that it's both) we will learn about the fundamental nature of morality - as humans perceive it; it's exactly this realization (that moral issues stem from interpretation by man) that will show that most things we consider 'moral issues' really aren't.
(the above may make it seem that I'm a moral relativist but I'm not - au contraire, once we peel away the human-induced layers of morality we will find the fundamental nature of it at the core)
However, this is not something that science can prove, at least without adding the claim that the only facts there are are physical facts. You're basically suggesting that we open up people's heads, look around, go "Nope, no norms here!" and take that to be evidence that they don't exist. This is problematic at best, since were they to exist, normative facts would seem to have properties quite at odds with physical facts, and your assertion starts to look question-begging.
Metaethics is not my area, so I'm afraid all of this is rather rough and ready, but the SEP article [1] is a pretty decent starting point.
[1] http://plato.stanford.edu/entries/metaethics/