Earlier quoted context omitted.
What should society do in that case? Absolutely nothing. Or more precisely: eliminate any remaining anti-voluntary laws. In a fully voluntary society, what "society should do" is a non-issue. As for individuals, they should do what they think is best. So some will think it's bad to hire X persons b/c they are, in fact, 3% worse at their jobs. And others will think it's bad if no X persons can get jobs, and will hire…
A clarifying example: Suppose the sexists are right, and women are poor programmers. They're okay students and can fight their way through an undergrad program, but give them a year or two in the workforce to come up to speed, and they never really develop an ability to attack hard problems. They just kind of flail at problems unproductively, rely on peers to bail them out, generally make a mess of the codebase, and…
Fundamentally, it's irrational to force people who disagree with you to do things your way if they don't see why it's best -- to make them go against their best judgment (also irrational to deny they have best judgment, attribute their ideas to things other than thought, and so deny the disagreement exists at all, and forcibly override them on that basis). The only rational thing to do if you want a (B) style world is persuade people, which is not at all the same as campaigning for laws to force people.
And by the way, straight, white, Christian males go to extraordinary and ridiculous lengths to prove themselves, all the time. For example, working super hard in school for 10 years to gain credentials. That's ridiculous and only loosely correlated to actual merit. And I, as someone who chose not to do that, have to prove myself in other ways, which can be hard sometimes, but so what? In general, proving yourself and gaining a reputation is a hard problem that does take effort to solve. And a system where people don't have to prove themselves to the satisfaction of their employers/clients/customers/spouses/friends/etc would be insane.