Maybe "misogyny" is the wrong word - too strong. Chauvinism might be better.
Regardless, it's an ingrained belief that, as men, we have a particular role and it can rustle our jimmies if that role is usurped in any way, even for our own good. The closer the person is to us that usurps that role and our belief that only we should make decisions about what we should know and what is best for us and our well being, the more we get rustled. However, we also believe that we are capable of making those decisions on behalf of someone else - particularly "our" women.
Think about it before you reject it out of hand - it's a well documented part of the male psyche. It's what drives us to arm ourselves to protect "our women" and families. If you don't believe it, do some reading on the psychological make up of men and women and our pre-programmed tendencies. They're real, whether you want to acknowledge them or not, and they impact our reactions to the things that happen to and around us. It isn't something that's malicious or evil, per se, but it can lead to us having a real hissy fit when we're left out of the loop about something that impacts us and can shade our reaction to the person that does that "to" us, ranging from feelings of disappointment to feelings of betrayal, and other points in between.
My reaction is disappointed understanding; that seems to be close to
Dessolos reaction as well;
Milton749, and many others, went for full-on betrayal. If she'd been fucking our best friend while in a relationship with us, that's betrayal; trying to protect us and help us have our best possible life - that's something that should be forgivable. I know Milt will still disagree - you don't see yourself in those terms and don't think that petty side is part of you, but it's part of all of us. When we acknowledge it, we can better deal with it. Or not.