Photographing things that are plainly visible from public spaces is a constitutional right.
If you are videotaping cops in public, carrying out “public functions,” it is your right to film them and there’s nothing they can legally do to stop you.
Obviously, you can’t legally interfere, and they have leeway determining what that means, but when recording from a reasonable distance, staying out of the scene, then police officers have no right to come over and stop you filming or take your camera.
There are no legal circumstances in which the cops can they destroy your film. Still cops will try. Cops try to confiscate and destroy people’s cameras and erase pictures all the time.
The ACLU’s “Know Your Rights” guide for photographers, lays out the legal protections for filming in public in the US. The guide cautions that cops ”may legitimately order citizens to cease activities that are truly interfering with legitimate law enforcement operations.”
What if you disagree with the cop and you want to continue?
Firmly and calmly remind the cop of your rights, while continuing to record.