Why are salaries so often considered confidential information? Why are employees often disciplined for discussing their pay? A lack of transparency is one of the reasons that unequal pay persists. Check out this article about the many consequences of these policies.
Since I was young, I have always been told never to discuss payment with another person inside or outside of the work place. It has always said to have been rude, but here in this instance, if I were one of the employee’s that felt as if they were facing gender discrimination and therefore making less money, I would ask a colleague (of a different gender) maybe what they were making or I would sneakily ask if they enjoyed their pay raise, acting as if I had received one too. I realize it seems unprofessional and it probably is, but if the company managers will not discuss the problem or if it even is a problem with you and are likely to fire you for bringing it up, then unprofessional might just be the only answer. Especially if the Supreme Court requires more evidence now than they used to.