This line of thinking knowingly and often unknowingly, feeds the repression of the female. It’s one thing to forgive, another to trust her entirely. I don’t think it’s shameful for pt to restate what has been widely researched. Now that women have easy access to birth control, they no longer have to worry about long term consequences. A study by oxford university found that having a long ring finger means you are statistically more promiscuous and more inclined to commit adultery. That’s not proof, of course in a sense of the scientific method. What you said just basically made you a traitor.
It doesn’t mean you deserve to be cheated on, but it’s a bit of psychology to say here, this is maybe why that happened. If they deny or don’t put any effort to rectify it, by all means, leave.