Think Progress's Matthew Yglesias has this post about, well, the title. There are a whole host of issues I have on the subject, which boils down to: women are paid less than men. So long as the phrase goes: "equal pay for equal work" I have no problem with it. In fact I am a huge fan of that notion. People who take more time off work for family issues (children, ailing parents, spouse, whatever) are NOT DOING EQUAL WORK. Now, that sounds mean, but to ask a company to pay two people the same amount when one is doing less work, is not payment equality, and it does not matter the gender, or age, or anything else that may be different between the two.
The trouble with family responsibilities discrimination is that it is a perfectly legitimate form of discrimination: paying someone who works less, less. Now, this does not mean that it is employed in a fair manner, but that is a much more complex issue as year over year percent increases compound, and many industries/companies don't use a linear scale anyway.
I appreciate that men can't get pregnant and so this is inherently unfair. But neither is it fair to compensate two people the same when one does more work. I am genuinely torn by the whole thing. Unlike some of my peers, I have no problem with, a university hiring a woman over an equally qualified man because of her gender. I don't really even have a problem if she is less quantitatively qualified, as measurable differences (# papers, impact factor of the journals, etc.) between two applicants for tenure-track positions are generally a crap method for hiring anyway, and basing it on gender is at least non-random. On the other hand, if it is a known policy to hire women over men (who are least equally qualified) then that places an excessive burden on those women to produce, and getting pregnant does have a tendency to be viewed as counter productive.
Again, the issue is very complicated.