choose the right breeder first --breeders belonging to breed clubs.
Go to shows meet breeders every puppy bred is not a show puppy they will have pet ones. Tell the breeder what you want a good breeder will be helpful
it is more likely the skin is already irritated thats why it is getting chewed
it could be hot spots , fleas even mange you will need to find the cause first
I have had this problem too. As soon as I see the other dog I tell them to leave it alone it's only a puppy (even if it is not) I stand still and let the other dog go past me when it's gone past tell them they are good