Your observations are limited to the scope of your life. I traveled around a lot growing up, but I spent most of my time in the southern United States until I came up to Vermont for college. I was shocked by how selfish people were, and half the time I thought I was just boring to death everyone I talked to. In reality, there are subtle, but key cultural differences between northern and southern social expectations.
The South is an "honor" culture, while the North is a "dignity" culture. The South is a "guess" culture, while the North is an "ask".
"Honor cultures place importance on socially conferred worth, reputation, and a positive social image, all of which can be granted or taken away by others."
"In contrast, dignity cultures place importance on context independent, individual, and inherent worth, which is less affected by the social regard of others."
"In some families, you grow up with the expectation that it's OK to ask for anything at all, but you gotta realize you might get no for an answer. This is Ask Culture."
"In Guess Culture, you avoid putting a request into words unless you're pretty sure the answer will be yes. Guess Culture depends on a tight net of shared expectations. A key skill is putting out delicate feelers."
People weren't being rude, nor did they hate me. They were just conforming to wildly different social expectations that drastically shaped how they interacted with me, and each other. In the South you smile when you talk to someone because that's how you signal engagement in the conversation. It was also crazy to me how many people responded to gestures of kindness with distrust. In the North, you ask if you want help. Offering, and people will think you want something from them. And for women, they'll think you're flirting with them.
Long-winded, I know. But the point I'm making is that you would be surprised by how much our culture influences our behavior, and how blind to that we can be until we step into another one, and really ask ourselves 'why?' There are certainly biological differences between men and women--most notably their different reproductive roles, and different balances of hormones--but there are many theories that explain how culture could account for current behavioral differences in socialization. Whether or not you believe a patriarchy still exists, hopefully you can agree that it did exist for a very long time in our history, and that it has left a powerful echo.
And, for the record, in my personal experiences with women they've tended to have more variety in their behaviors and opinions regarding sex (as well as everything else) then the homogeneity you describe.
EDIT: Fixed tenses.