If your employees are angry and think that they're not paid fairly, that's on the employer to fix. Either it's perceptual, and the employer needs to clarify something, or it's a real gap, and the employer is at fault. This article suggests that the solution is to continue not telling people what they are paid. I concede that humans have terrible judgement in many things. This is why it's absolutely necessary to be as transparent as possible. Tl;dr: If your employees are complaining about unequal pay, you're doing something wrong.