I think a couple of people have touched on something here that is something I'd consider first. If a child plays with a dog with a squeaky toy, it is very possible that the chick, especially if it was cheeping, was perceived as a squeaky toy and the dog wasn't actually out to kill the chick. Once it had the fuzziness or feathers of the chick in its mouth, it may have wondered "what the heck?" and shaken its head, thus flinging the chick. Or not. I wasn't there and didn't see. But, you cannot correct a dog for something it doesn't know it did. It has to understand first. It has to be taught that the chick is a living thing and not a toy -- IF the toy idea is what the problem is. When my kids were toddlers, they'd have their toys all over the living room. Toddler toys and dog toys are sometimes very similar. At the same time, the dogs would have their toys all over the floor, too. I successfully taught (within just a day or so) the dogs that the kids' toys were off limits.
My point is that, if the dog thought the chick was a toy, and if the dog usually plays with squeaky toys (or any toy) with a child, it hasn't done anything wrong. It has to be taught the difference. If it still grabs a chick and flings it after it has been given ample time, exposure and teaching, THEN it needs to be corrected.
Another thought that came to mind almost immediately is that dogs that are bred to hunt have a very high drive to do just that and even to kill. A cheeping chick is very likely to incite a dog that is meant to hunt, to follow its instinct and drive. It can be trained not to follow the instinct and drive, fortunately. It is no coincidence that squealing, running kids are often chased and even bitten by dogs. That behavior is often perceived as distressed prey by a dog. So, too, a cheeping chick or one that it flapping its wing(s).
There are a lot of good answers and ideas in this discussion. To me, it doesn't sound like dog was trying to be dominant.
It has occurred to me that by the time this thread settles down, the chicks won't be chicks anymore.
Very, very good points, thanks for your input.