Hummm, how many more people have I heard say that they trust their spouses.
Well, at least one more; I trust my spouse with good reason. You're missing a couple of other crucial elements that @Married but Happy
touched on - Respect, what I would term high self-esteem and feeling secure in the relationship.
My husband is really easy going, and hasn't got a jealous bone in his body, but I would hope and expect that he would say something if I was with a man who was flirting even though he trusts me. Its not appropriate behaviour.
I am all for good wise boundaries, and to feel a little jealous if there is reason to is perfectly normal.
I understand mate-guarding, it's just I've never been put in that situation. We walk into a restaurant and there are two responses. Some will give her a cursory glance but others will look her up and down clearly liking what they see. I know this because the very next thing they do is to check out who she's with. In the seventeen we've been together there's not been one occasion where a man has followed up on their interest when I'm with her.
So, as I've said I understand mate-guarding but never been in the situation where my wife would disrespect herself, our relationship and me by responding to someone flirting with her right in front of me to the point I'd have to step in. She is, after all, the wise woman who once said "I don't blame other women for wanting to sleep with my husband. I would only blame you (<-me)". It's not her job to police me or vice versa.
Of course, we both get hit on. I've been hit on with her standing right next to me, but we both think that it comes from women with low self-esteem who need the validation of being able to "turn a man's head" of someone who's clearly in a relationship. Her ex used to fall for that all the time. I consider myself better than being a temporary tool to boost some random woman's ego at the expense of my partner. You have to see these things for what they are. If I'm making my partner jealous then I'd consider that I wasn;t conducting myself as I should.
As for the possession thing, I'm not really comfortable about thinking of another human being as my possession (though I can see that as kinda romantic). She has my loyalty and that should be enough. And vice versa.