Obviously this is all anecdotal and not "scientific" compared with the study in the summary, but it should be clear that this problem of police violence is not going to be completely solved until the cultures of "shoot first and ask questions later" and "protect each other" within law enforcement are changed.
The study does not claim that cameras eliminate the problem. To quote the summary:
use-of-force by officers wearing cameras fell by 59%.
That's a good thing, even if it's not perfect. And it provides information to help understand when excesive force is being used, and provides evidence in cases when it is used. Unbiased evidence to help get to the actual truth. All of this is a Good Thing (tm).
Or should we let the perfect be the enemy of the good?