both sides have valid points and my guess is that the drone pilots were flying very low to take pictures and video. However, this video presents a very interesting and narrow legal issue: can the police demand i.d. when they have no reasonable suspicion that you have, are, or about to committ a crime? In most states, including NY, the answer is no.
If I was the cop, I would have said "yes, I have reasonable suspicion that you have committed a crime of recklessly endangering other's safety, including people and animals on that farm, by flying low over them, and have broken FAA rules, as codified in the CFR, by flying over people and not maintaining visual line of sight of the drone". The burden would then shift to the drone pilots to try to negate that with more than just a simple "no".
I'm not 100% positive they flew very low and out of VLOS, but if they got the farm's workers' attention, they were probably flying low enough...what's the rule, have to be above 200 feet over someone's private property? Aside from FAA rules, there are blanket rules about endangering someone's life, property, invading privacy in their own home or business, and the cops could have proceeded on suspicion of those violations.
In any event, had the officers have been a bit more educated on drones, they would have been able to articulate a probable cause or a reasonable suspicion, and mention that they need to confiscate the drones as evidence to review the video.
If it was me and I felt I've done nothing wrong, I would have showed my i.d. to just be on my way.