There are so many bad takes in this. But mostly, I think the author is internally inconsistent on multiple fronts.
In one paragraph she argues that the subjects of photos aren't upset by having their photo taken and then shared/promoted/published whatever.
> Over the years, many people I’ve photographed have found themselves either in publications or on Instagram. Almost everyone asked me to send them a copy, thanking me for the captured moment.
But later she says she fully expects that if she asked for consent after a photo is taken, it wouldn't be given.
> And asking for it afterwards almost guarantees you will be turned down. Even I, as a photographer, would feel suspicious if a stranger came up to me saying they just took my photo and would like some kind of retroactive permission.
This to me highlights that she's cherry-picking. Some subjects are fine with their picture being taken and shared. Great! But clearly this doesn't imply that all subjects are fine with it, and she knows this. If you're going to explicitly disregard some subject's "strong personal preferences" when they disagree with you, you don't get to use other subjects' acquiescence as any kind of evidence of an absence of harm.
She highlights a photographer who spent a year photographing a family through their windows, and say that though it was legal, "the ethics of what he was doing are certainly up for debate." But later she says "But for an action to transcend individual discomfort and enter the netherworld of immorality there has to be both a strong societal consensus as well as palpable, real-world harm resulting from it." So ... if the family didn't experience a "palpable, real-world harm", the photographer wasn't being unethical? Who gets to decide whether the harm was 'real-world'? Does she think that only if a domestic abuser is able to hunt down their ex or something that a subject has experienced any "harm"?
The author jumps from a lack of "palpable" harm to conclude "there is nothing inherently dangerous in the mere act of photographing people, children included, in the anonymity of a public space." "Unethical" and "inherently dangerous" are not the same, and a harm, which may or may not be "palpable" is that photography coupled with social media and instant sharable publishing can totally destroy the "anonymity of a public space" that she takes as a given. Have you experienced stage fright? If in a public space someone builds a stage around you, and places you before a digital audience, have you experienced harm? Have you fastidiously curated and cropped and tweaked images of yourself before putting them into particular public contexts? Do you experience a 'harm' if a photographer with a large following decides that the candid shot of you which they think will get the greatest audience response is not one that's flattering? Is that harm 'palpable'?
I think the understanding of "ethics" in this context has to switch from being about trying to establish "harm", and instead look a equity and power. The photographer sees an opportunity to benefit. Taking the photo followed by sharing and promotion may bolster the photographer's reputation, build their audience, even lead to financial benefit later. The photographer gets to exercise choice and control throughout the process -- which shot to use, how to crop it and manipulate it, in what context to show it. The subject has no control, likely enjoys no share in any benefit, and has the possibility to see various perhaps immaterial harms. It's unethical in part because it's inequitable; it's arranging one's own benefit at another person's possible expense -- and arguing then that the detriment to others isn't "palpable" or "real-world" is just minimizing so she can keep doing what she wants to do.
Yes it's legal. Often harms will be negligible. I'm not saying that street photographers are monsters. But as with any behavior with concentrated benefits (in this case to photographers) and diffuse costs (to subjects), of course the party that stands to gain is going to say they're doing nothing wrong -- and they're the least credible judge exactly because they have the most to gain.