They argue in the article that Google hires fairly from the pool of applicants, but that the pool of applicants often includes members of this religious sect because people employed at the company encourage their friends to apply, who are often also members of the sect.

If that is true, it isn't really Google's fault. If it's false, I doubt there will be any documentary evidence to say so - these people aren't stupid, they won't have said "make sure you only hire my religion" in an email.