“A third belief about males has both descriptive and normative forms. It is the belief that males are, or at least should be, tough. They are thought to be able to endure pain and other hardships better than women. Whether or not they do take pain and other hardships “like a man,” it is certainly thought that they should. When it is said that they should take pain and hardships “like a man,” the word “man” clearly means more than “adult male human,” but rather one who stoically, unflinchingly bears whatever pain or suffering he experiences, including that which is inflicted on him precisely because he is a “man.””

This is true even when he is not a man, but rather a boy. Boys are taught early that they must act like men. Crying, they are told, is what girls do. They are discouraged from expressing hurt, sadness, fear, disappointment, insecurity, embarrassment and other such emotions. It is because males are thought to be and are expected to be tough that they may be treated more harshly. Thus, corporal punishment and various other forms of harshness may be inflicted on them but often not on females, who are purportedly more sensitive.
Source: The Second Sexism: Discrimination Against Men and Boys (2012), Chapter 3, part 1: Beliefs about Males