My take on this:
"Naturally, the FA's warning bothered me and I felt the need
to explain myself."
Why? The only appropriate response to being informed that you are not permitted to take pictures in a non-public space is "I understand" or simply "Okay". No explanation is necessary as it won't change the rule that the flight attendant is likely obligated to enforce. However, the author feels compelled to justify himself rather than just let it be by saying:
"I want you to understand why I was taking pictures. I hope you
didn't think I was a terrorist. Here is my business card
[offering her one]. I write about United Airlines on an
almost-daily basis and the folks at United in Chicago are even
aware of my blog."
This is quite ambiguous. The flight attendant is probably thinking "Oh great, here's some critic who is going to scrutinize and complain about everything I do and then write about it publicly. If he's so notorious that the guys in Chicago are aware of him, he must be bad news. Is he telling me this to try and con me into letting him take more pictures? Some disgruntled self-important writer is the last thing I need...". Imagine how the response might have been different had he said:
"Sorry about taking that picture. I just want to say that I love
United and everything you guys do. I'm really excited about being
in BusinessFirst class on this new aircraft and wanted to capture
the moment. Thanks for letting me know about the photography
restriction, though. I respect that and won't take another
picture."
But again, that whole exchange should never have happened. Then later, this gem of a sentence:
"Me: That's a lie, captain."
Ouch. Now the only way to get your way is for both the captain and the flight attendant to lose face and admit that, yes, it was a lie. What was he expecting? That the captain brings the flight attendant over and asks her "Did you lie?" where she responds "Yes, Captain, I lied about this passenger taking additional pictures because I was afraid that he might write about a negative experience with me." I could go on with how the conversation with the captain should have gone, using face-saving phrases like "she may have been mistaken" and such, but at that point the battle was long since lost.
None of this excuses the flight attendant's alleged retaliatory action. However, having the situation escalate to that point could easily have been avoided.