Well, if the police have nothing to hide they have nothing to fear.
Most in the Slashdot crowd would scoff at using the "nothing to hide" argument as it applies to more widespread surveillance of ordinary citizens. At the same time, they would happily use it as a justification for more widespread "surveillance" (e.g., transparency and monitoring) of police, intelligence services, and government in general.
I do not think this is an example of doublethink, or a double standard. It's not a double standard if the situations it's being applied to are, in fact, different. There is a very big difference between the private matters of private citizens and the actions of government employees in the conduct of their public roles. For that reason, always-on police cameras seem quite reasonable, so long as they can be switched off or set aside as soon as the officer goes off duty and resumes being a private citizen.
Many of the arguments raised in debunking the "nothing to hide" argument are worth considering, and should guide the proper implementation of police cameras and other "watching the watchers" efforts. I don't, however, think the arguments are forceful enough for us to not implement police cameras, though.