It's been so long since the personnel world was normal that people forget: Married men are more productive and hard-working than unmarried men or women. George Gilder's Men and Marriage has excellent stats on this, and there are no doubt more recent sources, too.
Hiring is a process where you estimate future behavior as well as past experience and qualifications. That's why a married man, in the real world, gets extra points for being who he is.
Ignoring "life-style" factors in a hire is objectively insane, but employers are under immense legal and cultural pressure to pretend that a married man who lives in the suburbs and a single gal with a nose ring who lives in a bad part of Brooklyn and goes to clubs at night—who happen to have gone to the same college—are equally qualified. From an employer's point of view, she's more of a risk for being unreliable, but he's not supposed to take that into account.
The cultural logic of today's human-resources culture:
Failing to discriminate against men = artificially propping men up.
"It's been so long since the personnel world was normal that people forget: Married men are more productive and hard-working than unmarried men or women."
IMO your facts are right but conclusions are dead off.
What the modern personnel world is interested in is: will this employee complain or quit when we tell him to stay late, to come in weekends, to forget about holidays? Mr. "yes sir, anything you want sir, I didn't have any plans tonight besides sitting at home playing XBox" gets the promotion. How much extra expense will the company incur because this employee is not 25 but 35 or 45 or 55, not single but has a wife and kids on the insurance?
The facts that you correctly cite about better motivation and better work product aren't considered. It isn't just anti-male discrimination, it's a FUBAR prioritization of costs and benefits.