First, diversity, particularly in regards to race and gender, has become a cultural dogma, an idea to be pursued (never questioned) even if it comes at the expense of personal choice. Second, it is taken as gospel that the gender disparity in STEM fields stems (pun intended) from gender discrimination.
There is no doubt that sexism exists in this world. However, it is silly to assume that every disparity in numbers equates to sexism. Steelworkers are 98% men yet there is no outcry that the reason is because of sexism. Could it possibly be because (much) fewer women choose to be steelworkers? I suppose that jobs in STEM fields are considered more desirable and therefore there is more focus in those areas. However, isn't it within the realm of possibility that at least some of the discrepancy in male/female representation in those fields is due to personal choice and not discrimination? Is it at least possible that there are more men in the world who want those types of jobs than women? Should we really expect that men and women will want the same jobs in the same numbers all the time? Are we that much alike?
Don't get me wrong, sexism when and where it exists is a horrible thing. However, artificially trying to make a particular job have an equal number of women and men (which some companies are now trying) is not the way to solve that problem. In fact, it can be a form of sexism itself.