The results show that use of force and complaints are down. How is that the "exact opposite" of his theory? Maybe most of the complaints that were prevented would have been frivolous. Maybe most of the use of force that stopped would have been appropriate: I.e., the cameras cause those interacting with the police to behave better. Maybe most of the abuse is intentional: If that's the case, then there is nothing strange about hypothesis that the police intending to be abusive would also intend to turn off the cameras when they intend to be abusive.
There's no reason to assume that he "ignores real evidence".