Definition of Insured Bar to Coverage on HO

We have had a claim denied under a homeowners policy and would like your help in explaining the denial to our insured.

Here is what happened: our insured is currently using crutches to get around, and so is unable to walk her dogs. A neighbor volunteered to walk them for her. But in returning home, one dog slipped its leash and unexpectedly attacked our insured's young son. The little boy was severely bitten. We turned in a claim, since the policy says that under section II an insured “also means with respect to animals or watercraft to which this policy applies, any person or organization legally responsible for these animals.”