I'm sure Cordelia Fine is correct in her criticisms of some of the studies of sex difference. But what I am unconvinced about is when people cite the book as support for the position that there are no differences between male and female behavior and characteristics (...on average, across the population etc ...) which is not what CF claims.
I read the book with interest on MN recommendation, but was disappointed that it focuses so much on studies investigating cognitive differences (empathetic vs systematising etc...) and much less on the studies on the differences between what men and women are attracted to in seeking sexual partners, and what they will do to prove themselves attractive and to promote the survival of their offspring. I think this stuff is much more interesting and has more explanatory power for relations between the sexes than the marginal differences that Simon BC looks at.
But mainly I disagree with the underlying reasoning of Fine which is the same as the OP's friend - that if you believe there is a biological basis to the behavioural differences between men and women then you have to give up on feminism.
As CF says (in reply to S B-C) "The thesis of my book is that while social effects on sex differences are well-established, spurious results, poor methodologies and untested assumptions mean we don't yet
know whether, on average, males and females are born differently predisposed to systemizing versus
empathising. I therefore argue that to slam the door in the face of those who aspire to sex equality is premature."
I think it is a mistake, both in reasoning and tactics to think that if robust studies did show differences in the genetic disposition of men and women towards ambition, risk taking, systematising or whatever, then it would be "the right time" to slam the door in the face of efforts towards equality and non-discrimination.
Why on earth should that be?