I normally agree with you Amy, but I'm with the LW. I'm sure you know better than most of us how engrossing "talking shop" can be with someone who shares your ambitions or field of work and sometimes you get so engrossed you don't realize the passage of time. I also think it's kind of lame when a grown person brings up "you were making me look bad in front of my buddies"...unless of course she really WAS in the other dude's lap.
With all that being said, it shouldn't have lead to the LW being defensive: how hard is it just to say "I'm sorry, I got engrossed talking to Henry about photography and didn't realize it was coming off as flirting."?

Being gracious in the face of adversity (like being accused of doing something you didn't) goes a long way towards diffusing a situation. So what bellflower suggests could undo a misunderstanding in short order, without fanning any flames. In the long run, I don't think it would hurt the LW any.

Hmmm, reminds me of an encounter at a party years ago. I had been chatting up a girl for a while, when her (unknown to me bf) comes over and starts going into us about flirting.
She tells him, we weren't flirting, just talking. I interrupt, apologized to him and basically said what was she talking about We had been flirting, or at least I had definitely been.
I don't know if she was super oblivious or just pretending to be. Either way I lost any interest and deleted her number.

So another aspect of this is, was photography guy flirting with her and her being oblivious or receptive.

so... let's flip this around, LW:

You are at a party with Boyo, and he's TOTALLY flirting with the bartender, and she keeps doing that little thing with her hair, and mixing him drinks...
and upon leaving the bar, you say to him: "it was humiliating that you were flirting with this good-looking bartender in front of all of my friends..."

And upon further reflection, he says: "That girl is a professional bartender, and I was just asking for some tips. I'm annoyed because I don't think I did anything wrong."

Now. How does it feel to you to have your feelings dismissed so casually?

Who's feelings are impacted here, regardless of the innocence of the situation?

Instead of being annoyed, maybe a bit 'o contrition is in order.

It is possible to accidentally hurt someone you love. So, do you say: "it annoys me that you took that wrong"?

Probably if he was actually insecure, he would have injected himself into your conversation, as a mate-guarding move...

But he didn't, so this actually mighta smarted a bit, even if you didn't mean anything by it...

I've known women over the years that feel like the warmth of the sn when they are paying attention to you, and it feels cold when they turn their eyes away. Even platonically, when they are talking to you, you are the only person in the room to them. SO, this is where Amy's demonstrable behavior is important. Even something as simple as saying to Photo-guy: "You have to meet my boyfriend! and dragging him over there... says a million things to every person in the room.

Without saying one word.
Go plunk down on his lap and make sure he knows that he is the only guy for you... and make sure in the future to think outside yourself, about how interactions look to other people.

There may come a time, when he accidentally hurts your feelings too... hopefully you will both try to patch that up, then as now.

Joe: So another aspect of this is, was photography guy flirting with her and her being oblivious or receptive.

Since she said she was "just asking for some tips" then, to take her word for it, she wasn't being receptive.

But if he is straight and she is attractive & sexy, then he surely was flirting with her (and you know exactly what kind of tip he wanted to give her.)

It's difficult to judge what 'really happened' from the short explanation, but it doesn't mean a guy is "insecure" just because he was annoyed that you flirted with a good-looking guy in front of him and his friends. Actually that seems like a fairly normal emotionally healthy reaction. (Though again, difficult to really judge without details.)

Being a "social butterfly" doesn't mean you get to do what you want with no consideration for other people's feelings. I think it just takes a little consideration and respect for the person you're with to tone it down a little and consider how something can come across ... e.g. if my wife's around, and me and some other girl are starting to get a bit flirty, I dial it back, because I consider and respect her feelings.

Doing it in front of his friends adds a bit of public humiliation to the mix - maybe you didn't mean it that way, but it comes across as a sort of 'I don't care for my bf's feelings, I'll flirt with other guys, he's wrapped around my finger' type message. Maybe this isn't you, but I've met too many 'social butterfly' types who indeed turn out to be cheaters.