There two issues here. The dogs death and the arrest of the owner. I fail to see any law broken by the owner, thus no need for an arrest. A unlawful arrest caused a dog to react defensively, which resulted in a officer shooting it.
I guarantee you that the dog was not reacting because he was in agreement with your uninformed legal opinion.
They're allowed to stop on suspicion, handcuff, and pat down. And they can hold you on suspicion. Suspicion of obstruction of justice when his sound system was interfering, he was told to turn it down, and he responded defiantly, is pretty much there.
I still think it could have de-escalated if the owner had been allowed to leash him. Suspect was cooperating.
That wasn't really cooperation, it was submission under protest. To uncuff him so he can deal with the situation shows that you're weak in regard to it. Let him loose and he might think that, with the situation out of control, now's his chance to turn on the cops and finally "win."
The guy had a huge chip on his shoulder. You can't take the chance on the hope that his attitude suddenly did a complete 180. Humans are opportunists, and you never really know what might suddenly click in their minds as an opportunity.
They had control over him, and his cooperation wasn't guaranteed, so you don't gain more control by lessening control.
Doubtful he'd try anything surrounded cops, some of them with SMGs.
Guns don't mean shit if you can't use them. The cops are not allowed to just shoot anyone they don't like. There are rules. So, from a cop's perspective, it ain't a tool of control.
Your hands are for control. Pepper spray/taser/beating them with your PR-24 is for control. Your gun is for safety.