Singer isn't special. He is merely more frank than most about the evil beliefs at the core of modernist dogmas, and more willing to take those ideas to their logical conclusions. Other liberals harbor the same evil beliefs, although they may be less willing to express them or to face what they mean.
Some years back when our handicapped son was still alive and well, my wife encountered a highly placed bureaucrat (at the Department of Education) with similar perspective. He did not stand out as uncommon, but one in a crowd of similar ilk. To my wife he coldly explained his position as if it were the only possible way to reason. My wife responded with equal coldness that she could bring our son there and see which of these bureaucratic intellectuals would be willing to carry out their brilliant reasoning and dispatch our son, themselves.
They were, well, shocked!