One reason diversity initiatives are sabotaged?
If you think it is valid & right that your subgroup represents and defines a category, for instance, men considering themselves the rightful prototypical members of STEM careers, you will be more likely to resist opening up the group to others and more likely to demand that anyone entering the category conforms to YOUR norms.
This effect is reversed when you do not have a baseline belief that your group has the default right to be the prototype