should be payed. That's the crux. I don't think anyone disagrees that the majority of the gender gap is due men and women doing different jobs, on average. Its just that not everyone thinks the causality is one-way.
No two persons can be evaluated to be of equal value, and have equal pay, especially in expert positions (which CS mostly is). And if gender correlates with pay differences, that means that gender discrimination is happening.
Or that the one sex is better than the other at that particular job. But with the quality of the work being extremely difficult to measure objectively, we can only assume the former.
There is no point in sticking your head in the sand by saying the gender gap is illegal to uphold. It won't change status quo.