the thing i have a problem with is that feminism is not a group. it's a concept. the way it affects people is consequential; asserting that it's invalid because of the way some people express it isn't a sound way to judge its worth. the same can be said for religion, politics, etc. because they all function in the same way. a body of ideas is created and expanded, and people absorb and express those ideas individually in unique ways, and eventually, it probably becomes part of culture.
i don't find it a compelling argument against feminism (or x idea) when people say, "look at this guy who was a real jerk," because him being a jerk is completely irrelevant to the ideas at hand. that's an issue with ol' buddy guy's personality, not a problem with his source of inspiration.
let me phrase that differently:
i don't believe any feminist truly thinks that women = men
it's just an opinion.
you're making a (very bold and broad) claim and will be expected to substantiate it