This is one of my biggest pet peeves when watching other people's kids.

Whenever a child gets a bruise or a scratch, it's like a big freakin' deal.
Parents do not understand that just because their child gets a little bump or bruise when I am there does not equate that I am a careless caregiver. It just means that they experienced what a typical child experiences in a typical day and it happens when they are around as well. Yet when in the presence of a nanny, for some reason it "has" to be the nanny's fault somehow.

You can sit down and address the issue further, but if there are cultural issues here, it may be more difficult to come to an understanding since cultural differences are next to impossible to compromise on.

Everyone is quite ethnocentric.