Police be like

Bonus meme :

It should be legal on a national level to film any and all public service workers (while on the job)

I work in municipal government, but a LOT of what I do involves working with privileged information. Not my information or the city's information, but private people and company's information.
You're welcome to submit an open records request and I'll be gladly release what I can. But sometimes information needs to be redacted and kept private for privacy or security reasons.
Why
- Great question! If it's illegal to film a public servant then it is illegal to verify they are actually serving the public's best interest. In particular if you catch a public servant performing amoral or otherwise corrupt behaviour there is no way to publicaly verify that. Further without explicit legal protections for things then it is easier for that action to be banned or otherwise made illegal. No protection is no protection. A corrupt public servant has a vested interest in misinterpreting law in order to prevent you from exposing them. Which is why Oklahoma's ban on filming police is still bad even though it is framed under the guise of protecting police from harassment
- Because your word means nothing vs the word of a cop and there are too many lying bastards out there wearing a uniform.

Some cop was trying to use his position as a cop to get 5 free loaves of bread, and the bakery guy was like: "Hey person's name get the camera, and post it titled 'the police stealing from citizens'" and the cop was like : "yeah, uhh... escapes with his partner".

Nobody likes to be filmed in public. Go up to a Walmart worker and wave a camera in their face and they won't be happy either. ACAB, of course, but not because cops are people who don't want to be recorded 24/7.