This doesn't sit right with me. A species does not exist based on something as brittle as some ego-stroking social contract. Apes have the same genital layout as us, and I doubt they have the same unconscious desire to maintain this alleged facade of masculinity. They, and we, have made it this far with this apparent Achilles heel.

No, it's more likely that the groin is not an Achilles heel. It's more plausible that we have the ability to protect that area, quite readily, given that it is quite necessary to do so in order to reproduce, and that a threat can come from beyond the species.

Any failure to defend the groin is likely an artificial one, induced by the expectation of a regulated sport, or a situation where the fight is more about dominance than incapacitation. Even in the latter situation, outrage is more likely to be at disregard for the purpose of the fight than that the offender has suddenly dropped the veil on masculinity as a whole.

I'm no professor of sociology, and I am a man, so maybe the brainwashing has gotten to me, but I found the explanation a stretch at best.