In the U.S., and maybe elsewhere, there's a long tradition of sissifying the upper class - most recently, and absurdly, Bush did it to Kerry in 2004. Teddy Roosevelt spent much of his life trying to change that image.
[WS:] I do not think so, upper classes are generally portrayed as strong and powerful, both physically and mentally, and only occasionally benevolent. The sissification is merely a populist caricature of the upper classes.
I think that a better explanation of the prevalence of machismo is the level of social integration or cohesiveness of a social group. Machismo seems to thrive in groups that either very low or very high on social integration, but is less prevalent in groups with moderate level of integration. The concept of social integration was first proposed by the French sociologist Emile Durkheim and initiated the type of analysis that has been the most successful in explaining delinquent social behavior.
The low integration condition creates intense competition among individuals for resources, safety and status. Machismo is simply an outgrowth of that competition and a signal to potential rivals - "I am tough, do not fuck with me" - which is a rational adaptation to the ever present threat from competitors. It can also provide a basis for male bonding, and thus some rudimentary forms of social solidarity that otherwise would be absent. An example would be ghetto subcultures in the US.
The high integration condition often creates highly scripted social roles and hierarchies that are often based on gender characteristics. As a result men and women tend to be "scripted" to display "proper" gender characters e.g. aggressiveness, domination, and strength in males and submission, weakness and protectiveness in females. In this situation, a failure to enact those prescribed roles may result in shunning and ostracism, which is an ultimate personal failure. An example would be certain Asian cultures, like China or Japan.
However, a moderate level of social integration eliminates the war of all against all condition characteristic of low integration societies, and thus the need for "defensive machismo," but at the same time does not fall into rigidly prescribed social roles, and thus does not develop the "prescribed machismo."