It is just as likely that female professors are more likely to respond to female questions because they expect that females are more likely than males to listen to the answer. Why do we have to jump right to a presumption of negative sexual bias?
It's still 'sexism' if a professor responds better to female students than male students because he perceives female students as being more receptive and grateful for the help. But not necessarily in a negative "I'm hoping to get laid" sort of way.
We generally agree.
Track record.