Serious answer: because their vision of masculinity comes with a hierarchy, and part of how you establish and defend your place in the hierarchy is to enforce the "rules" of masculinity while punishing others for being insufficiently masculine.
It's inherently insecure by design.
Serious question, why are conservative men so obsessed with how masculine other men are? Why do they think that endlessly thinking and talking about other men is somehow a signal of their own manliness? Why are they constantly nervously looking over their shoulders in a flop sweat?
