oh gosh.. that is really horrible. like everyone else is saying, don't sell yourself short, ever! i every walk of life people will take advantage of you, and this profession is no exception. you have to treat your business with a business mind.
personally, i would terminate if a child ever smeared feces all over the place. i couldn't deal with cleaning it up and part of having my ow business is that i don't have to. YOU call the shots here! embrace that power!