What a self-serving load of bovine excrement!
The question "why would I trust you, you didn't have a camera on?" is at the very core of 21st century policing: why _should_ we trust the police?
Yeah, it would be spiffy nice if we did (at least, nice for them), but since it is almost axiomatic (worldwide) that the police will close ranks around an accused cop, it seems entirely reasonable to insist that they provide the structure to justify trust, rather than simply demand special credibility based solely on their natty headgear.
And when a cop wrings her hands and worries that the poor widdle coppers might be unjustly accused, one wonders what freakin' planet she's been living on! The rest of us have to deal with (the risk of) unjust accusations, so in actuality the appropriate response must be "welcome to the club, boys in blue!".