Ok I'm a Nursery Nurse, NNEB, Nanny, I don't mind what you call me - I look after other peoples [and my own] children, and have done for 25 years.
If you feel that strongly put it in the contract.
The nurturing and care of the child, the love and understanding of the child, the want to be with the child is the most important feature of anyone working with children.
If someone didn't want to cook fresh fish, I'd cook it on their day off [assuming you're not so stuck in the 1800's that you allow a day off], some people love the fact they have 'staff', and are able to bark orders to them in a way they would never get away with anywhere else in society.
When their children grow up and tell them they loved their Nanny more then them they'll wonder why - because they just don't get it.
Respect is a double edged sword, if you can do a better job of raising your child, then do it yourself. Many people find the job this the hardest job of all,because it is, but slag off those who do it so well they choose to take it on as a career.
I've seen it before, worked for people like it before and no doubt will carry on doing so. Don't kid yourself that we don't all laugh about it, we see the mess you make of it all when we get back to work - and you're children are more loyal to us, and tell us all about 'when Mummy shouted at Daddy because she didn't realise the steriliser didn't wash the bottles too'!!