I don’t really understand the rationale behind protecting video/photographic footage taken in public.
The issue isn't about the right of privacy of those photographed in public, the issue/problem is what you feel like is and what should be protected information gathered by the media. The fear of media attorneys and watch dog groups is if this is allowed, what's to stop the police from getting information about a source if that source said something publicly, or wherever these slippery slope conversations end up. The media, like attorneys, clergy, doctors, counselors, etc. receive privileged information. There are plenty of people who think that unreleased footage should fall under that privileged umbrella.
The fact that it happened publicly shouldn't make any difference. Even though it happened in public, that doesn't mean the cops are entitled to have it. Their investigations shouldn't entail shaking down media, counselors, etc. If a client told an attorney privileged information in a coffee shop, should that information be available to be subpoenaed because there was a chance that the guy cleaning the tables may have heard what was said?