This is a fun way to make tourists feel insecure.

Call them out, where you wait on a foreign police, prove your identity, file a report -- in a non native accent / language -- in the best case...

or in the worst case, where they'll take you where you don't want to go (or other cabs to pickup), potentially drive off in a dangerous way as you forcibly exit the vehicle, and blacklist you from other cars

-- all while you're hoping to make it to a hotel, airport, tour safely and on time.