Discrimination of women
means that the women possess whatever discrimination we are talking about. It is a perfectly fine phrase when we are talking about an attribute frequently exhibited by women.
If, however, what we are talking about is male discrimination that adversely affects women, it represents a prejudice possessed by men rather women and an activity that operates against women’s interests. Now we want
Discrimination against women
Part of the problem is that the word “discrimination” has come to have both a favorable and unfavorable meaning.
“Discrimination” may mean the ability to see subtle differences, to distinguish between the meritorious and the meretricious. Such an ability may be possessed by someone.
“Discrimination” may also mean the activity of making life difficult for someone by reason of that person’s membership in some specific group. An activity can not be possessed.
The lawyers used to distinguish the second meaning by using the terms such as “adverse discrimination against a protected group,” but the adjectives have got lost over the decades.