I never said he was the bad guy. Never.
Here's what gets me and always does. Men and women do this all the time. They meet someone and the sex is absolutely burn the paint of the walls incredible. It's so good that the neighbors need a cigarette. Then they learn that when it comes to fidelity and monogamy, this person is not so good at that. In fact they're terrible at it and doubtfully will never be good at it.
So, this guy marries this woman and expects a different result. A different result despite placing her in the exact same environment, a soldier on deployment, where she cheated the last time. And, on top of that, he says it's okay to Play, but just limitedly. He's not a bad guy, but he is not realistic.
She's unrealistic too for marrying into expectations that she cannot meet.
If I have gasoline and a lit torch, you're going to have fire no matter how much the gasoline and the torch promise not to start a blaze.