TulliusCicero is saying that the 60s and 70s were the period when women entered those fields en masse. Hence you should compare the state of those fields in the 60s/70s to the CS field now if you wanna determine sexism as the cause of entering/not-entering a given field.
It's implied by saying that those other fields made serious efforts to combat sexism back then, but CS hasn't made an equivalent effort now. What other reason would there be for such a discrepancy, other than being motivated by sexism?
