Patriarchy absolutely teaches us that. It’s part of enforcing heteronormativity in men - if you find another man attractive or beautiful, you cannot express that without being accused of being gay, and this seeps into our self conception where not only do we have trouble viewing ourselves as capable of being beautiful, but we aggressively police men and boys around us who we perceive to be seeking beauty themselves.

There’s been movement on this in the younger generation, but it’s still the hegemonic attitude.