The word "nihilism" seems to live a double life, in a way that I think sheds light on the basic error in thinking which underlies moral realism.
On one hand, nihilism can simply mean the position that there are no ultimate values, that nothing is objectively good or bad, right or wrong. In this sense, I am a nihilist.
On the other hand, nihilism can mean a lack of values altogether, so that the nihilist has no real commitments and cares for nothing but manipulating circumstances for the sake of his or her own gratification. This is a kind of animal that I definitely am not, and hope never to become.
I think some people assume that the first meaning of nihilism listed above is synonymous with, or somehow leads to, the second. This is not the case, and I think I can say why very clearly and concisely; I do have values, but I do not hold them just because of something I believe to be true.
I am deeply committed to truth, freedom, love, empathy, compassion, fairness, enjoyment, appreciation, desire, creativity, and other qualities that I think of as making up a good human life, but I do not believe any of these things are good or right in the same way that I believe (for example) massive bodies attract each other according to an inverse square law to an extremely good approximation.
I hold the values that I do for reasons that are too numerous and complex for me to try to summarize in a brief post, but I understand that the reasons for my holding these values are not exhausted by empirical observations, logical arguments, and authoritative instruction, and if someone else holds values contrary to mine, it is not necessarily because one of us is wrong about about something. The sources of our values are not in the outside world; they are within us, and we are responsible for the values we hold and for what we do on their behalf. This is one of my most important beliefs, and it's something I'm going to elaborate on a great deal in the future.
So, in a rather trivial and artificial sense, but a sense that might hold weight with some people, I can rightly be called a nihilist. In a deeper, more interesting sense, I am anything but. I think it's important to understand that a lack of belief in objective value is far from implying a lack of values altogether.