"what does that mean?" I couldn't come up with an answer for that
This seems to fit the definition of cargo cult.
You clearly had good intentions, but you can't go around saying phrases without being able to back them up. This should be familiar to you from technical situations - consider: "prefer composition over inheritance" - reasonable advice, but be prepared to explain yourself, not just parrot it.
It's contextually a lot different though. In this case, it's not that he didn't have an answer or a means to clarify, it's that, based on her initial reaction, he didn't have one he wasn't sure would dig a deeper hole.
I doubt anyone out there will have a similar visceral reaction to discussing code architecture.
I disagree. I can think of many ways to clarify the remark in a manner that I personally wouldn't see anything wrong with. At the same time, I can imagine a person intent on outrage finding a reason to be mad about any one of them. I generally assume that people I'm engaged with professionally aren't looking for opportunities to be mad.
Its subjective. Personally, I don't think it's reasonable to become upset by a single comment, made with good intentions, as happened in the story, certainly not upset enough to want professional consequences for the other party.
Even a single comment made with ill intent I don't think would push me all the way to pursuing professional recourse, not without me trying to 'fix' things on my own first.
This seems to fit the definition of cargo cult.
You clearly had good intentions, but you can't go around saying phrases without being able to back them up. This should be familiar to you from technical situations - consider: "prefer composition over inheritance" - reasonable advice, but be prepared to explain yourself, not just parrot it.