I see the libertarian nutjobs are having a party today, well let's use my Economics Abitur some:
If it would happen at only one company the argument "find another job" would work, the problem is, it isn't just one company but ALL of them. That's because greed knows no honor or morality, and wanting to turn a profit is greed. If you don't think so, take a good look at the world, or study basic economics.
Let's say it wasn't equal pay, but equal pricing. Let's say a company that makes water makes the decision to take 1.30 monetary units from every male customer and 1.50 monetary units from every female customer. Most of us would deem this to be disgusting, simply because it would be. Let's change that product from water to condoms - still everybody disgusted? Probably not. Now you could argue by morality - call it slut profit - if she wants it this bad, she's gonna have to pay extra.
All these examples you can argue with should be legal, because a woman could simply buy her condoms/water from another producer - the problem is: they all do this. In this case the laws of supply and demand would be changed by what doesn't have anything to do with the supply or the demand, but the part were they both meet - the pricing.
Before somebody accuses others of not knowing economics, check your damn theory. It is common knowledge that pay is and can be determined by the laws of supply and demand. A culture in which it is believed that even though women work the same there work is inherently worth less than a man's work, is manipulating the laws of supply and demand, the same way unequal pricing would manipulate the marked, unequal pay manipulates the market.
If a woman works less in the same job (30h instead of 40h) she should of course be paid less, but that's because she isn't working the same amount of hours. If a woman and a man work on provision and the woman sells less units (doubtful), of course she should get less, 'coz she sold less. But if your only reason is "she agreed to it" or "she's gonna have family anyway" that's just high-end BS [commonly knwon as libertarianism].