After I wrote the question, I realized that it sounded like a challenge and could provoke a defensive response. I even started writing (and not just thinking about) a note afterwards along these lines: "I know this question sounds like a simplistic challenge, but I really do mean it as a good-faith question." I'm not sure why I decided against including that line.

I was genuinely surprised by the apparent certainty with which you made the statement, as opposed to something like: "brain lady believes that x," or even: "in brain lady's considerable experience, she's found that x." I should have known better; I know you think critically about these things and that it's probably for the sake of brevity that that you don't painstakingly qualify every statement you make about NFB (or talk therapy, or meds).

FWIW, I don't chalk this up to you being hyper-defensive, but to me not being careful in conveying tone.