feminism is about gender equality from a very specific perspective on society, namely one that assumes the existence of patriarchy.

The concept of patriarchy arose within a certain branch of feminism, and tho it's permeated it's not a fundamental concept to feminism per se.

it's disingenuous to decide that because someone thinks something you don't feel is very liberal they're suddenly a secret conservative even though they're life-long democrats who've always supported liberal causes.

Well, to characterize anyone as liberal, conservative, or whatever is necessarily going to be a generalization. Capitalist libertarians are hard for so many people to grasp because they tend to be "liberal" on social issues and "conservative" on economic issues. Hence, it's useful to have a seperate term to describe them, because there are so many people that can be characterized that way. Maybe what we need is a new term to for people who tend towards what's usually considered to be liberal positions, except on identity issues.