It doesn't just look like systematic discrimination, it is. Most people agree that there should be equality, but how do you get true equality in the system you described? Without introducing a positive bias into the system it will not change. Women need equal opportunity and positive discrimination (affirmative action, incentives, social pressure, whatever you want to call it) is a way to balance out the negative discrimination and create that.
Note that I'm only advocating equal opportunity, not equal numbers.
By "systematic discrimination" I guess I meant it in terms of stated policy. i.e. It is already illegal to discriminate in the workplace based on sex. But, as I've already said, the discrimination is seldom a simple matter of "she's a woman, and therefore will suck". It's more complex, and there is no way to root out intrinsic, personal prejudices without internal change, i.e. a changing of culture.
Opportunity is determined by the needs of the employer, and if they need something that they believe men will better be able to provide (a competitive spirit, aggression, forcefulness, stereotyped masculine traits) it is not discrimination based on sex, it is discrimination based on personality/ability (which is how people judge things anyway). The overall effect will be the same, but legally, it is impossible to sue unless the employer actually states "males only". This means that "equal" opportunity is impossible without changing corporate/business/academic/any male dominated workplace.
That is the reason why I believe that a cultural revolution that promotes a well-rounded, diverse organisation is necessary.
The flip-side is that for industries/jobs such as kindergarten education and nursing/baby-sitting, the proportion of males in these jobs are astoundingly low. I can bet you that they don't have "equal" opportunity either, because employers will look on with suspicion at males who would want to be in close proximity with young children.