Not sure why the page wouldn't let me finish that one, but if you're still reading . . . no, it's not wrong to be angry. You have the right to be furious. You're right, the sheer irony of a woman who's telling her husband she wants no sex and then going to someone else for a sleazy affair on the side is maddening.
BUT . . . you're also right that if you want to fix this, you have to find a way past that anger. You have no control over how you feel, but you control what you do. I think what you mean by "is it wrong to be angry" is something like "Is it wrong to nag her about this and complain all the time about the injustice of it?"
And the answer is . . . yes. If there's whining and moaning about the injustice of her to be done, do it here. When you talk to her about how much she's hurt you, it should be from a position of strength and confidence. That's easy to say and very, very, very hard to do, unfortunately, but you can do it. And again, this is a safe place to vent.