I had that happen to me a few years ago. I was in a busy, crowded street with my bike, and I got off the bike and just wheeled it through the town because it was a rush hour time and there was traffic slowing down and people crossing the road, etc. As I walked past a crowded bus stop, two girls stood there and one deliberately pointed right at me and burst out laughing. Her friend looked up at me and didn't laugh, as if she saw me as if to say ''what's so funny about her?'' She was right - there wasn't anything funny about me. I don't display any unusual traits, and even if I did display anything minor, they would be too minor to notice in a crowded town with lots going on. It was a hot, sunny afternoon so I was in a good mood too, therefore wasn't feeling stressed or nervous.
I think pointing right at someone and bursting out laughing for no apparent reason is very rude and unacceptable indeed (unless it's a joke with your friends/family, but that's different). But random strangers doing it at other random strangers in public is so droll. Even if I see somebody who does stand out, I still have no intention of pointing and laughing at them, even if they're funny. If I found them that funny, I just laugh inwardly in disguise so that they wouldn't know. It is none of my business anyway.
I'd thought NTs would know better not to point and laugh at people in public. 
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Female