I think the biggest point is that ongoing anger at an ex is corrosive to yourself. Sure, it may be helpful to some in the beginning to get up and out of a situation that isn't good. But eventually bitterness and anger corrupt your own life. That doesn't mean you have to say your ex wasn't wrong in what they did. But maybe just accepting that they're a smaller person than you thought and letting go of the need to see them punished.
