Refreshingly, Steven Pinker believes in the humanity's ability to cope with truth. The truth he focuses on is that the blank-slate hypothesis is absurd but compelling to whose who seek an easy way to justify or generate the latest fads in political correctness or incorrectness without risking the heavy lifting of rigorous thinking. Pinker argues that scientific truths, whatever they might be, carry no moral imperative. To think otherwise is the naturalistic fallacy. Nor should one confuse one's tastes with morality; to moralise tastes is to sanction violence (i.e., the gratuitous seizure of freedoms) against the individuals whose tastes differ.
Pinker summarises the commonalities between fascism and (the ideology of) Marxism. Both claim the necessity of a violent fight of "us" (Arians or the proletariat) against "them" in order to install the natural order (Social Darwinism or communism), with "us" at the top, thus allegedly maximising the social welfare function by exterminating the inferior others. Both ideologies err in putting the idea before the man. Both ideologies rely on the human tendency to partitions others into an ingroup and an outgroup, thereby courting a negative-sum game where a positive-sum game would have profited all. Marxism, in addition, appeals to the blank-slate hypothesis to justify the stability of the destination state.
At best, an ideology is a scientific theory based on a 300-year-old evidence. At worst, an ideology is a system of beliefs that, to many, feels good to hold and that subjugates those many for the gain of the scheming few. Ideologies feed on the social science that is not methodologically individualistic and whose tenets are thus hard to observe and disprove. Methodologically individualistic social science, by contrast, is easier to discipline by observation and to interface with other sciences, such as biology, neuroscience, and psychology.
Pinker's reasoning is beautiful. He seeks simple fundamental principles, and then tries to explain as much as he can by appealing to these principles. He is not scared of what reasoning may uncover.