Yes, I'm not advocating biting the nose off people who make clueless remark, but you were wondering what could be the use of looking back on forty-year-old sexism and criticizing it. From a historical and philosophical point of view, I think that attitude is necessary, not in order to make us feel superior to what people thought before, which would be stupid, but so we can remind ourselves where we come from and precisely how we will (hopefully) be looked at fifty years from now.
Intentions are well and good, but they are if not the basis then at least the weapon of all kinds of paternalism. Taking them into account is good; they shouldn't be an excuse.