CCC is a private event and does not fall within the purview of the right to public photography.
Anyway, I don’t go to CCC to take pictures of people - although this is an unfortunate policy because it means that the culture of CCC is not recorded for posterity …
I think it would be a better policy for CCC to require photographers to wear a special easily recognized t-shirt or funny hat, so that they could take pictures of crowds but give non-participants time to dissent.
It’s a breath of fresh air IMHO to be at places far away from any desire for posterity. Just remember yourself what you’ve seen instead of outsourcing that job to your phone for a while.
For those of us who are aphantasiac, it is not possible to remember what we have seen ourselves.
The camera and sketchpad are the only options we have.
And while I have the utmost of empathy for your condition, that is unfortunately not a compelling reason to generally allow to violate the privacy of everyone else.
A good variant of that would be to ask participants to wear an "opt in" signal, so we don't end up in a situation where people are burdened by having to repeatedly decline photographers' requests for photos.