I'm not expressing an opinion on the idea, just outlining the debate for you.
That is a super optimistic view of software engineering hiring. Hiring is a disaster and a crapshoot, and everyone knows it; don't pretend that processes with certain demographic qualities (any demographic qualities, honestly) are somehow rigorous. You hire based on a brief interview and some algorithmic trivia people forgot from college, or you give up on that and decide that hiring based on where someone went to school or who referred them to you is higher-quality.
1. does github in fact "only hire women and minorities" at the expense of superior, talented white men?
2. assuming #1 is true, what evidence is there that said hiring practices are at the root of their financial difficulties?
It's easy to throw out loaded statements. I don't think it's nuts to request clarification.