He says a very odd thing about atheism, and I'm not sure if I'm just reading it wrong, or if he was just unclear in what he was saying.
First, he says "atheism is 'disbelief in, or denial of, the existence of a God.'" Fair enough. But then he goes on to say this (emphasis mine): "As a statement about the universe, agnosticism would seem to be the most rational position to take because, by the criteria of science and reason, God is an unknowable concept. As a statement about one's personal belief, however, I assume that there is no God and I live my life according, which makes me an atheist, although I prefer to call myself a skeptic. Why? Words matter and labels carry baggage. Most people equate "atheist" not only with someone who believes that there is no God (which is technically not a tenable position because one cannot prove that there is no God; that is, you can't prove a negative), but also associate it with communism, socialism, or extreme liberalism.
Is he saying that atheism is an invalid position on its own merits, or by virtue of the baggage that it carries with it in society? He admits to being an atheist, both here and elsewhere, so I'm a little confused why he muddies the waters here.
I personally read him as saying that it is untenable to say "I believe that there is no God." That just doesn't make sense, in light of his own definition and admission. Again, the continuum between statements of belief and statements of knowledge is slippery.