<uncharacteristic anger>
Uncontrolled dogs are a menace almost any way you look at it, from pooping in your garden to killing your livestock. Or you.
Expecially when they pack up.
A "180 pound" Great Dane is a pack all by itself, and probably outweighed Grandma, who was visiting, and not the dog's normal "human control." To me, this was akin to handing Grandma a cocked .357 without any instruction, and letting her roam free.
You don't go kicking dogs or "grabbing their collar" to separate them especially if the fight is so one-sided and blood has already been tasted. Chances are too great that you will get bitten yourself. If you have chemical deterrents, they're worth a try, but I would not go sticking my own paws in a fight like that.
As far as the LEO's (or any ordinary citizen's) dog is concerned, the law seem to conveniently forget that one's pet is not merely property, but is a member of the family, loved as such, and cared for as such. To my mind, the same instinctual protective reaction-set should apply.
I think too much was made of the guy being an LEO. In this particular case, he should be regarded as any other plain ordinary person permitted to carry concealed.
And that pic of the kid resting near the Great Dane is akin to presenting pictures of recent ne'er-do-wells as innocent smooth-faced little boys --I'm sure you know whom I mean.
</uncharacteristic anger>