Social Conservatives are not the only ones with a pessimistic view of human nature

A paragraph in this interesting review caught my attention:

The articles by Savulescu and Greely are fascinating but, I think, troubling. Although they reply to objections from social conservative critics of the practices that they (with some qualifications) endorse, there is no substitute for having social conservatives speak for themselves. I find the articles in this volume insufficiently skeptical of the ability of human beings to react beneficently under conditions of unprecedented power and moral uncertainty. A rejoinder from a social conservative would be a welcome addition to the volume.

Why would the "social conservative" have a monopoly on being "skeptical of the ability of human beings to react beneficently under conditions of unprecedented power and moral uncertainty?" Let's leave aside the empirical fact that there are plenty of social conservatives that end up endorsing social engineering projects of various kinds and let's grant that some non-social conservatives remain optimistic about human nature endowed with absolute power. But non social conservatives discovered, say, Liberalism of Fear (Berlin, Shklar, etc) a while ago.