Women truly do get paid less than men. Number of hours worked, marital status, number of kids, none of that accounts for the difference in pay. Women really are getting paid less and the only explanation left is discrimination.
As Arthur Conan Doyle’s famous detective Sherlock Holmes famously said*, “when you have eliminated the impossible, whatever remains, however improbable, must be the truth.” Researchers have looked at all of the other potential explanations for this gap in wages. As much as it might annoy Alex Castellanos to have someone tell him this, he is wrong. There are not other factors that explain it away and show that the wage gap isn’t the result of discrimination. People are actually paying their female employees less. Females are aware of this problem. Denying that this problem exists and voting against attempts to remedy the problem are part of why Republicans are stuck with this “war on women” thing. (Only part, there are many, more deliberate and intentional policies that are also part of it).
* He also said variations on this quote like “Eliminate all other factors, and the one which remains must be the truth” “when all other contingencies fail, whatever remains, however improbable, must be the truth” and “when you have excluded the impossible, whatever remains, however improbable, must be the truth.”