Newsworthiness is already a defense in some parts of law. It is a matter worked out by society through cases over time. I know I'm talking to someone who hasn't studied law much so I'll just say you can read a lot about this when you study it, especially the history of constitutional law. But you could start with the idea that it is an event that later might be subject to debate or controversy.

Yes, chat app users could be fined if they identifiably capture the images of strangers (but, as you know, it is not required to video strangers in order to use chat apps). You would sometimes know and sometimes not, like many crimes, but it provides recourse for those affected and chills those who would otherwise do it without considering the effect on others.