Eh, everyone looks stupid in the video. Walking around with a rifle on your shoulder on a normal day looks stupid, even if it is legal. Cops usually have to show up to respond to calls. They don't have to stick around after they determine that nobody has broken the law. They certainly don't have to lecture people with their opinions or poor grasp of laws. That looks stupid too.
Cop keeps telling him he's not under arrest. Arrest = "depriving a person of their personal liberty of movement." He might not have cuffed & stuffed the guys but I would think that holding them at gunpoint and preventing them from leaving even though there was no indication of a crime was arrest.