The purpose of marriage has been historically oppressive.
advocating same sex marriage means masking the historical disempowerment of women and calling it "equality"
To the extent that heterosexual marriage is an institution profoundly implicated in the historical disempowerment of women, some feminists extend this indictment to same-sex marriage, regarding it as a “sell out” incapable of rehabilitation, and unworthy of queer struggle. For feminists, the question of lesbian and gay marriage is, or should be, inextricably bound to the ongoing critique of marriage as an institution. That critique originates in the theoretical and practical indictment of all social institutions, built upon inequality and exclusion, which function as tools of male dominance.