The phrase "benevolent sexism" is not an oxymoron though. "Women should stay at home with the kids because they're so nurturing" is a belief that leads to reduced opportunities for women, despite ostensibly being praise of their inherent characteristics. At its simplest definition, "privilege" just means that a particular trait won't be the cause of things being harder for you, and by the example of women being nurturing, that's clearly not an example of privilege.