They will remove a child from a plane if the parents cannot calm their child and thats just for the noise. If you take your child the Drs office i don't think it would be ok for the child to be tugging at crutchs. The vets office is a place of bussiness it should be a controlled enviroment, the staff or mother were the ones who allowed the situation to get out of control, the man was just protecting his property.
I would not of swatted the child but i would of grabbed him/her and kept them out of reach of my animal, i've had to do that when i was rehabbing GSD dogs or just my regular friendly dogs. The parents may not like it, but the option is their child learns by getting bit, (my GSD rehabs were always muzzled) I don't see how i could be faulted for protecting their child. MOO