I found this comment on Jezebel in reading about The Daily Show's Lady Problem. In the comments, one person was torn between considering sexism and also purely hiring people on merit. One person responded:
At the beginning and early middle of the 20th century, most orchestral performers were male, with conductors and managers hiring based purely on playing ability.
After the auditioning system was changed so that all auditions were conducted with the players behind a screen, the amount of women in orchestras expanded to such a great deal that within about three decades many orchestras were majority female.
Merit is not very accurately measured. Especially in the performing arts.
I find this anecdote concisely describes the influence of sexism and how it affects the way we judge merit. Fascinating.