Maybe it comes from the idea that down through the ages masculinity is related to being the warrior, the fighter? Physically competitive? For which, I assume, a certain level of angry energy is required. The caveman mentality. Ready to knock anybody over the head with a club. Like in that Kenny Rogers song where he says, "Sometimes you gotta fight when you're a man" - which isn't really about being the sensitive intellectual type, but more about being masculine = angry, violent! Haha.

It's a good question...