> Just remind them, public photography is not a crime, and that there is no right to privacy in the public sphere, and why don’t they just smile and enjoy the fact that they are frozen in time on some strangers device, just like a strangers memory they have no right to erase. This is the needed context.

Hacker events are not public places and they are free to set different rules on photography. Considering it's a privacy and counterculture thing their aversion is pretty understandable IMO.