Masculine is the generic gender. Feminine is referring to a specific thing that is feminine.
For example, if there are a group of girls with one boy, the entire group is masculine. It is only feminine if it is completely girls; same thing here.
I understand the two words are not necessarily synonymous, but wouldn't it be idiomatic to translate the first part as 'Yes, it is obvious'? Or are we really talking about logical in a more mathematical sense?