Actually ...
I really want to listen to players, so I need to think of something related to feminism as a cause for superhero adventure. My head is bit empty with this one, give me something to grasp please :-/
I'm going to approach this from an entirely different angle than anyone else so far, not because there haven't been decent ideas, but because I like to get extra creative with ideas. I also agree with Wik, who noted that you must make sure everyone else in the group is interested in the plot as well: I think my suggestion has a possibility of giving everyone an angle to be involved.
Religion is both too easy and too boring a target, not to mention potentially problematic.
In one of the major cities in your campaign, have a woman with the resources to get her message out appear on the scene, suddenly covered by local news media and holding rallies and the like. She's a modern-day Phyllis Schlafly type, but with dangerously more charisma. Wrapping her message in things that sound comforting and un-threatening, our villainess exhorts people to a return to "simpler times", when women were less interested in getting ahead in the workplace and more interested in making sure their children were being raised properly and their spouses and significant others happy. Every household needs a breadwinner, sure -- and that can even be a woman -- but according to her "research", men can't be entrusted with tasks like raising children due to their more militant natures. Her message seems to be strangely entrancing to both women AND men within the civilian population.
Unfortunately, not only does our villainess believe that women don't belong in the superhero business -- she has the means to make her vision a reality via two different super abilities: while she comes off as just a normal human being, she is in fact a supervillain.
People without abilities are susceptible to her speeches, beginning to adopt some of her messages in their own lives, and are more susceptible to it the more they run into her talking on their TVs and in their neighborhoods. And people WITH superpowers can have them temporarily turned off by the supervillainess' touch -- or nearby presence -- and the longer you're around her, the longer it takes for those powers to come back.
This villainess is essentially the most dangerous anti-feminist: a woman with an agenda to make superwomen un-super, and to sway non-supers to support her cause.
The men in the party can be given ample reasons to be interested in stopping her: she can target a hero ally of theirs, rendering him powerless Stepford husband ... or brainwash a civilian friend under their protection. Or, she can just turn one of their powers off for a limited time.
![Wink ;) ;)](data:image/gif;base64,R0lGODlhAQABAIAAAAAAAP///yH5BAEAAAAALAAAAAABAAEAAAIBRAA7)