My sister's kids are both autistic, and as a result most of my nephew's friends are similarly autistic, or ADHD, etc. I totally get that sometimes as a parent you really can't do anything.
My sister told me about one of my nephew's therapists, who was in a store with her child. Her child was screaming and crying and there was nothing she could do so she was waiting it out. Another lady came up to her and said "excuse me, but I think *I* can help calm your child down." Rather than tell her to go fuck herself, the therapist decided this would be funny and said "please. Go right ahead."
The lady proceeded to try speaking calmly to this screaming little girl. The little girl wouldn't even look at her. Didn't respond to a thing the lady said. Eyes shut screaming red faced and crying. It was like she wasn't even there. Finally the woman gave up and said something along the lines of "well, I give up. Your child simply cannot be reasoned with."
To which the therapist replied "She's deaf." and walked away