Have you ever seen a child throwing a fit in public and though that the parent wasn't doing their job or that the child was just a brat?

I have an 8 year old autistic nephew. He has no verbal communication skills. Sometimes when my sister has been at the store, my nephew has gotten frustraited about something and started crying or throwing a good old fit. People look at her like she is a monster or somthing. I’ve even heard comments like “If she spanked his ass he’d stop doing that”. I have tried to take the time to explain what his condition is and some have appologized and some have looked at me like I was nuts. What is the first thing that you think when you see a kid throwing a fit? Do you think the kid is a brat or do you think he/she could have a medical condition?