"in public".
It's actually a public event, though, inside a building.
You buy admission to enter but it is still a public event. It's offered to anyone who can purchase a ticket quick enough.
Thus, they are allowed to set photography rules of which the rules are that photography is allowed. You being at a public event have no expectation of privacy meaning you cannot demand that no one take a photo of you because it's public.
You are extremely confused on multiple topics and seem to have merged several together for some reason.
For example, you're not allowed to take pictures/video in movie theaters because of piracy laws of which do not apply to expectations of privacy in public. Some museums also have piracy laws in place due to the nature of the exhibits or some conflated argument about "bright flashes damaging artwork". Some banks and other high security institutions post "no photography" signs because of security concerns of which are legal to do so as banks are NOT considered public.
In the end: if someone disagrees with the photography rules that have no legal basis in any public event than they are perfectly allowed to disregard them due to again it being a public event and people have no expectation of privacy at a public event.
Since you are not understanding concepts here's some links to help you.
recording of Motion pictures in a Motion picture exhibition facility
There ya go hope that helps a lot, and remember if you are at a public event or within the general public you have no legal right to dictate someone may or may not photograph you as you have no expectation of privacy what so ever even if the public event is held at a business.
If you don't like being possibly photographed by the public than it's probably a good idea for you to not go out into the public rather than demand everyone else cater to your outrageously over bloated ego. You aren't that special. You aren't that important. You don't get to dictate what others can do in public that they are legally allowed to do. Get over yourself.