Doesn't make a whole lotta sense to me. Sounds like a local stitch up. Probably had enemies on the force. If he wanted to partake in a prostitute, he could have just asked his deputy chief a report on anti-prostitution enforcement in his district, and made aware of all sting operations.
There's a lot more to this story than meets the eye. Also, the fact that he was fired so soon after being charged, instead of simply being suspended, even without pay, means to me that this was a set-up. If he beats the charge, there's going to be some massive lawsuit against the city.