I've been thinking about what we could do, and I believe the only angle we can take is the accountability of the public trust. Don't get me wrong, I don't have any trust issues with the police doing their duties, but stuff does happen, and if we have to rely on their own departments for evidence against their own people, that's where I start to have doubts. We do have body cams on most officers around here now too, but still, they do "fail" and video/audio recordings still do "disappear".
Another benefit I think is officer safety in a way. Of course they don't want to public to interfere with law enforcement, but I've heard officers suffer gunshot wounds or wreck their cruisers when help is 10+ mins away. Alot of scanner enthusiasts are public safety personnel, and could render assistance if they happen to be closer.
And personally, I feel safer being able to listen to law enforcement. When I see the plane up circling, I know they're looking for criminals, and I want to be aware of what's going on around my family.
I'm sure I'll catch some flak for what I said, but that's just my viewpoint.