Public events can implement rules too. I never said they didn't have rules. I just think it's retarded to go to any event in spaces that you don't own expecting to not end up on a camera. I don't think it's reasonable to say it's indecent to take photos at such events either unless the rules expressly prohibit it. Everyone went knowing the rules.
You don't have to like it, but I just don't think it's indecent to take a photo of a crowd if the rules allow it and everyone there is choosing to be there with their faces exposed.