Where's the "like" button? You've hit the big point with your next to last sentence: most administrators will back you all the way...until a parent starts making threats...then they fold like a deck of cards.

I once had an issue with a parent. It got to the point that she said "I'm gonna talk to the principal about you; what do you think about that?". I think she expected me to wilt like an old flower, instead I said, "Do it. I triple dog dare you". Principal never heard from her.

I wish more administrators had the guts to call the bluff.