Whether it's Ghost Busters, Mad Max, or Dr. Who I can't imagine the mindset that goes into "But it's a woman!" rants.
All movies and television need tension. What's better than a woman (seemingly inferior in strength, fighting ability - some would say intelligence - etc.) against a perceived evil?
That's the most tension you can get.
I really wish this wasn't news.
Also, the best action flick of all time is basically a treatise on the fear, responsibility, and horror of being a mom.