It's not a specific woman or a specific man. This sentence is referring to women and men in general. Hope that helps!
In my opinion, "The woman likes polite men" would be "Người phụ nữ thích đàn ông lịch sự".
But would the woman likes polite men be the same?
As Felix said, what makes this plural?
it isn't plural, it is general
The way English handles abstract concepts. In English, if you are talking about a category of Thing, you make it plural. In Vietnamese, you remove the classifier.
Such interesting etymology!
Having been through things = knowing the way of the world = being civil and polite!