What annoys you most about people?

I am finding myself getting increasingly more intolerant of people who form opinions about my child without even taking the time to get to know what’s wrong with him.

Today we are in the supermarket (he hates crowds and I refuse to give into this and make him go, he will have to look after himself one day) he decided that he wants to push his baby brother in the trolley, so with my assistance I allowed this to happen. So he is happily trolleying along and bumping into everything, but smiling and the distraction of the people around is great. So I am chatting away to my other son and watching Zac as he scoots around and isle, then bumps head long into a young woman and her daughter (who was around 7 same age as my son), then the next thing I know she is yelling at my son, who promptly puts his hands over his ears and does what he always does when he is stressed and that’s scream at a high pitch tone. Well this leads to her starting to yell at me about him being stupid and screaming like a baby, whilst she is shouting at me, I am trying to apologise and move on dragging Zac out of the situation, but she is having none of it and starts calling him names, so again I am finding myself apologising and trying to explain he is autistic not stupid and he understands what she is saying…...a total blank from this woman, at which point I have a baby crying a screaming and very stressed child and a mother having a tantrum about how my son almost killed her child.
I had enough and the staff were starting to notice so I told her one more time I was very sorry and promptly dragged my children away trying to calm a very upset baby and child! Do people like this pick because they see the weakness? This would never have happened if it had been just myself and my other son as I know the first apology would have been enough?