Earlier quoted context omitted.
The author is a tech lawyer. I think the article is there to start discussion. I agree with him that if private venues allow people to record like this they should offer, at the very least, an opt out. "Purple lanyard" seems like a good way. It's also a pretty easy spot in post production where you can either blur or cut as appropriate.
There is a super obvious opt out that doesn't require people to take special actions. Don't go to places that allow recording.
I occasionally see people saying “well, if you don’t want to be in photos published online, don’t be in public spaces”.
This is nonsense, for a number of reasons. Clearly, one should be able to exist in society, including going outside one’s own home, without needing to accept this kind of thing.
In any case, here, the issue is somewhat different, since it is a private site, where people engage in private activity (a hobby).