The problem with gender and sexual essentialisms is not whether or not there are essential differences between men and women, males and females. Certainly there are. The problem is the politics of determining the relative social value of these essential differences between the sexes. The problem is whether or not essential biological differences lead to essential differences between woman-people and man-people that lead to some people being presumed essentially better than others.
If there are essential differences, the erroneous presumption made by gender feminists is that individual woman-people must be better at some things than individual man-people and vice versa. If essential differences between man-people and woman-people do exist then change is impossible for individuals, since the differences between woman-people and man-people are essential, like oxygen is essential to water and chlorine is essential to salt. And for the majority of human history essentialism has, in fact, been used to relegate individual women to a diminished social status. So gender feminists have every reason to be paranoid about essentialisms that may diminish women's social value. It is better to misrepresent essentialism, to the detriment of innocent boys, than take the risk of being intellectually honest.
The problem of gender feminists' misrepresentation of essentialism is also one of degree. They wildly exaggerate essential differences. If woman-people are essentially different than man-people, the reality is that these differences are relatively minor and only show up statistically. The entire lunacy of the essentialism debate, as alluded to by Christina Hoff Sommers' The War Against Boys, hinges on an intentional misrepresentation of individuals as identical with the groups into which individuals are categorized. Certainly the gender categories of “man” and “woman” include many individuals who fit into these categories by definition alone. We need merely think of the difficulty of categorizing transgendered people to see how tenuous the man-people and woman-people categories can become.