Gloria Steinem wrote an amusing article titled: If Men Could Menstrate. You can link to the full text
or just enjoy this excerpt:
So what would happen if suddenly, magically, men could menstruate and women could not?
Clearly, menstruation would become an enviable, worthy, masculine event:
Men would brag about how long and how much.
Young boys would talk about it as the envied beginning of manhood. Gifts, religious ceremonies, family dinners, and stag parties would mark the day.
To prevent monthly work loss among the powerful, Congress would fund a National Institute of Dysmenorrhea. Doctors would research little about heart attacks, from which men would be hormonally protected, but everything about cramps.
Sanitary supplies would be federally funded and free. Of course, some men would still pay for the prestige of such commercial brands as Paul Newman Tampons, Muhammad Ali's Rope-a-Dope Pads, John Wayne Maxi Pads, and Joe Namath Jock Shields- "For Those Light Bachelor Days."
Statistical surveys would show that men did better in sports and won more Olympic medals during their periods.
Generals, right-wing politicians, and religious fundamentalists would cite menstruation ("men-struation") as proof that only men could serve God and country in combat ("You have to give blood to take blood"), occupy high political office ("Can women be properly fierce without a monthly cycle governed by the planet Mars?"), be priests, ministers, God Himself ("He gave this blood for our sins"), or rabbis ("Without a monthly purge of impurities, women are unclean").
Male liberals and radicals, however, would insist that women are equal, just different; and that any woman could join their ranks if only she were willing to recognize the primacy of menstrual rights ("Everything else is a single issue") or self-inflict a major wound every month ("You must give blood for the revolution").
Street guys would invent slang ("He's a three-pad man") and "give fives" on the corner with some exchenge like, "Man you lookin' good!"
"Yeah, man, I'm on the rag!"