I'm in my mid-20s. I don't often see my parents, but when I'm out with my mother, I'll ocasionally point in excitement at someone or something I saw that interests me. My mother always disapproves of this, and she always says "don't do that, it's rude to point" in a sharp tone. Is she right?
Pointing at people can be considered rude, especially if it's just individuals going about their business. My understanding is that this rudeness is because it can make the people you're pointing at feel self-conscious. However, if it's people engaging in an activity (e.g. clown making balloon animals, a bunch of people drawing on the sidewalk with chalk together, skateboarders doing cool tricks, etc) then IMO it's not typically rude; there's less of an implication of judgement and more of an acknowledgment that the activity is out-of-the-ordinary.
Pointing at things definitely isn't rude at all. You're not going to make the awesome ACAB graffiti self-conscious.
If your mother's the sort of person who doesn't like having attention called to her, or if she seems like she'd take being pointed at in public to mean "someone thinks I'm doing something wrong" or "did I sit in wet paint? or spill on my shirt?" it could just be her feeling extra sensitive on behalf of the people being pointed at.