Accountability literally means "being forced to give an account of your decisions", i.e. explain the reasons behind why you made the choices you did. The idea is that when you have a public forum of people with common values, merely being forced to explain yourself will activate mechanisms of shame, guilt, and conformism that keep people inline. Otherwise you'll face the judgment of your peers.
This mechanism breaks down when your peers don't hold common values. If nobody agrees on what right and wrong are, you just find different peers until somebody thinks that what you're doing is right. Or you just don't care and figure solipsism vs. the status quo is just a matter of degree.