"Feminism" doesn't mean "defending women from attacks".
As to your theme, liberals don't rush to the defense of Palin for the same reason that Conservatives didn't rush to the defense of Fluke.
Actually, Republicans don't criticize Fluke for the same reason that Democrats criticize Palin.
Fluke demanded that government confiscate money and redistribute it. Palin is a female who is defying the Democratic party, and Democrats destroy all women who dare not be Democrat lest other women get in in their heads they are free to support their conscience. There is no comparison.