It's not the gun, it's the camera that got him upset ...
Police, patrolling on their own, frequently draw their weapons when it comes to stopping people, often at the end of a loudspeaker and locking their fingers behind their heads, lying on the ground, etc. in the US of A. The police often handcuff a topped person 'for their own safety' (the civilian's and not the Plod's).
I took up using a motorcycle in a very, very busy city of 12,000,000 people where the driving is simply atrocious about 5 years ago. When foreigners are involved in collisions they are invariably expected to pay irrespective of guilt, made more difficult as numerous 'witnesses' come forward to testify against the foreigner.
I fitted an Oregon Scientific waterproof minicam to my helmet, concealed in a moulded fibre glass 'lump' on my helmet; I have never been held responsible for payment of any damages by the police since using it. The traffic police love seeing my accident videos. On a few occasions I have been stopped for bribery collection, by police, for driving in a car lane as opposed to a motorcycle lane and on every occasion when the police became aware of the camera they have simply returned my money and said Go!
Seems that the Plod, in the West, think they have more rights and privileges than the public and whilst they can video anything with impunity, the Plod get very uptight when the public pulls a 'Rodney King' clip of taping the Plod doing illegal things.
I hope this motorcyclist does the 'American thing' and sues for wrongful arrest.