Big difference is. When a human goes after you, you suffer some bruises.
When a dog goes after you, especially a dog that size, he can severely injure and kill in a blink.
Owner was an idiot, because from the cell phone sound, it sounds like he was told before hand to leave. You can hear the guys in the background laughing at him that the cops are coming back to get him. And when the cop has an assault rifle in hand, and there is an RV on site (Die Hard anyone), that means it's a highly dangerous situation.
Don't blame the cops one bit for what they did.