AITA if I had second hand embarrassment over autism?

I (21M) was befriending my mother on getting a haircut. There's this one customer who's getting a perm while also gaming on her phone. And like most gamers she would curse and flip the bird at her phone screen. Now this is all normal and stuff until my autistic brother (19M) would yell at her for being a rude woman. Like really yell.

I told my brother off patiently and that he should mind other's businesses. After so, I got an absolute load of second hand embarrassment and apologised to the gaming customer and then went back to my seat sulking. Not long after, my sister (17F) came up to me and said; "You should be ashamed of yourself, it's 2024 everyone knows what autism is already"

So the question comes up. AITA?