They're not speaking as a teacher, but as a person with integrity, someone who endeavors to tell only the truth, especially in a situation as grave as the discipline of a child under their watch.
Yes, I understand. After all, I am paying for their professional, expert advice about my child and I want to give it due consideration. Nonetheless, I want to give my child a fair chance to explain her side too. If I do not do that, I fear that it will alienate my child from me. So I seek her opinion. Of course, once I hear her side, I will not trust her blindly either.
The very act of doing this seems to irritate the author - which I find very disturbing. Trust, but verify, is the principle here.
I already said the profession wasn't part of the consideration.
Asking the child if what the teacher said is true is seen as an affront on the author's character as a person, not as a teacher, so it's reasonable for them to take offense at the accusation.
It's entirely reasonable not to trust the teacher's authority by default--I'm not challenging that. I'm only defending the author's position on taking offense to being challenged on something that was just said.
The very act of doing this seems to irritate the author - which I find very disturbing. Trust, but verify, is the principle here.