40 years in California, I'd only ever been assaulted by dogs a handful of times and that's because they weren't controlled. Dogs are generally allowed to run freely in their own yards/homes so it makes sense that strangers/police entering yards and homes in a stressful situation, encounter aggressive animals much more frequently.
I am expected to uncritically believe the owners, to believe that all these dogs are harmless and well trained and that they're all being shot for no reason. Well I believe that some of them are being shot for no good reason, but I've seen very little to suggest that most are. And from my interactions with the general public, I am inclined to believe most dogs are, if not dangerous, then at least poorly trained.