I'm sure everyone here expects me to support the parents on this one, but this is a case where I cannot.
My midwife, who is open to all sorts of traditional and nontraditional stuff, absolutely believes in testing her clients for GBS. If the culture is positive, then she approaches it first from an herbal standpoint, which has proven to be highly effective in her practice. (I can ask her what her protocol is if anyone is interested.) If that doesn't work, I think she next goes to antibiotics.
Given that she is a homebirth midwife who is so alternative, it says a lot to me that she believes in prenatal GBS testing. So my husband and I opted for it.
Now, perhaps this family treated herbally for it and didn't say anything? I think that some sort of treatment is appropriate, though statistically speaking, the odds remain very low that the child will become sick.
I do not agree with a practitioner mistreating or threatening a patient/client because they don't agree with their choice. That is unethical. You present the pros and cons, make sure informed consent is had, then you treat them like an adult and let them make the choice. It isn't your child. I can certainly see the frustration in watching a client make a choice you wouldn't, but that's part of medicine and midwifery.
Just my $0.02.