You seem to assume that prejudice and discrimination are not reasons for lack if diversity in tech, rather than other factors. Affirmative action may be a blunt and ineffective solution to fight a lack of diversity caused by prejudice, but to be fair any discussion of its merits must recognize that it's purpose is remedy discrimination, not just to improve diversity in a population.

Yes, affirmative action makes a big assumption when it posits that a lack of diversity is caused by prejudice. But might that not be the case, that often a lack of diversity is caused by prejudice that can most easily be countered by a directly oppositional force? To be fair, it is this assumption that must be challenged when you challenge affirmative action.