Feminism isn't just for women's sake. The war on patriarchy is for the good of both sexes and all genders, and to the detriment of no one but jerks.
The patriarchy harms more than just women: it also harms men who refuse to conform to the masculine stereotype it needs to propagate to justify its continued exploitation of women. Really the only people it tangibly benefits are assholes. And if there's any man it benefits who's not an asshole already, well, power corrupts, as it always does, and the system thereby makes him an asshole. Unless he's an incorruptible saint, in which case, good on him. But not everyone is an incorruptible saint, no matter which sex one should choose to examine. (Now, I'm aware there are some so-called feminists who despise all men, and seek female supremacy, as opposed to equality. They aren't the ones I'm talking about, nor do I agree with them or support them.) No one rides this old horse anymore, but it's been set in motion, it's remained in motion for centuries, and it will remain in motion evermore, unless we take the uncomfortable task upon ourselves of laying it to rest.