Driver cuts off part of finger to prove he's not a black cab

We always thought it looked kind of cool in old Yakuza/Triad gang movies, but when we actually hear about people cutting off their own fingers to prove a point, we're a little more disturbed than excited. A driver was caught in one of Shanghai's recent black cab dragnets, where police officers pretend to hire cars illegally functioning as cabs, and then fine them.

Looks like they're doing a pretty terrible job: chinaSMACK has a pretty insane writeup of a similar situation, including a transcript of the police's interrogation, where the driver is tricked into picking up an undercover cop who said his stomach hurt. He is then violently arrested and accused of being an illegal cab.

By the transcript, it looks like a Chinese police interrogation would be enough to drive anyone insane, but don't you think cutting part of your finger off is a bit draconian for someone pleading innocence?