Why couldn't the guy just say "ok cuff me, lets sort this out at the police station". 
Because cops are pricks through and through. Their reply will always be "we need to consider everyone a threat until they are in cuffs"
I was cuffed when pulled over for speeding and ended up having a non valid drivers license. I was so utterly calm with the cop too. He asked me to step out of the car, I POLITELY asked "let me guess, I am being arrested". He sternly said yes and then said in an even shorter tone to step out of the car, NOW. Told me to turn around, I said I will get in the back of the car with no problem...no need to cuff me (again, politely). He said to not tell him his job. Total prick.
You wonder what would have happened if the guy knew a little more BJJ and ended up turning around and mounting the cop. The cop did not have a body triangle on him. The guy had it right in some way by keeping his chin in the elbow of the cops arm.