Organize on the basis of Motherhood?

I thought the idea of women being able to mobilize strictly on a basis of shared gender experiences (motherhood, in particular) was an interesting one. Ruddick essentially argues that maternal thinking is the antithesis to violence, and therefore should be investigated as it pertains to nonviolence in politics. Coincidentally, one of the student panels I attended last Tuesday for the PSA conference referenced a similar phenomenon currently unfolding in Japan. The "mothers of Fukushima" are a group of women who have used their status as mothers to protest in a way that would ordinarily be seen as more threatening by the state. They essentially make their arguments against the dangers of nucler reactors from their platform as mothers, as nuclear disastors (radiation poisoning, be it through air, water, soil, ect..) statistically effect them more than adult men. However, at some point you have to ask what is the cost of uniting as mothers. Although its wonderful that women have found a political voice in the patriarchal society, it essentially discounts women who can't have children, who don't want children, identify themselves as lesbians, and so on. Therefore in even being able to voice their opinions they are reaffirming the only gender roles that the government finds favorable enough to be used in protest. It's hard to say whether its worth having a voice as this cost, and whether these women are not complacent in their male defined roles as they recognize and intentionally use the fact that as mothers they are treated differently in society...or if organizing themselves soley on the basis of motherhood actually limits what they will be able to accomplish in the long run.