I think you are seeing an admixture of (1) misguided "altruism", and (2) the droppings of a certain cultural influence.
Imagine a girl's on a date with a man who is being genuinely abusive.
In this case, many -- if not most -- people would see no wrong with a man interceding and trying to take her off the dude's hands.
I mean, the more "traditional" way would be to punch the dude's lights out, but, I don't think very many people would see the wrong in just swooping in, out-smooth-ing the dude, and taking the girl away with sheer Don Juan mojo.
What you MIGHT be seeing, here, is someone who thinks the woman is just bored out of her mind, or offended, or "under-compensated" in any of 10,000 other ways.
So, someone thinks he's "saving" her from that. In the same way he might save her from actual abuse... just, i dunno, a lite version.
You remember that whole "pick-up artist" thing that was a thing, about 10 years ago?
Anyways, that whole thing came from this book ("The Game").
Among other things, the book described situations in which these "pick-up artists" would specifically look for girls who were out with other guys, and try to pick them off.
I think the theory was something like, "make the other dude do most of the pre-foreplay work", or something like that. LOL But, anyway, enough people read that book that people REALLY STARTED DOING THAT -- more often than you might think -- in bars across America.
As you might imagine, the results were almost invariably less than stellar, and often violent. Lmao. But, yeah, that was a thing. A thing that happened. And is probably still happening, as cultural left-overs, in some places.
In any case, no matter what, if you are seeing this then some dude is making a snap judgment that he's able to out-man yr man. That judgment might be absolutely, horribly wrong, for any of myriad reasons -- but, that judgment has been made.
I mean, trust me.
If someone is doing this, it will NEVER be the kind of super-old-fashioned cavalier-retro-gentleman who's totally up for a big challenge and a duel if necessary. LOL
Nope. It's someone who THINKS he sees easy prey. Why? Who knows. Yr man may want to think about that, though... because, for SOME reason, he's giving off a vibe that says "My woman's steal-able."
I mean, this has NEVER happened to me in 16 years with my husband -- a man who looks just as scrappy and street as he is. Never. Even though he's almost 3" shorter than me.