You need to say that DS has been upset for a week, and that you do not want them to repeat that method of getting him to lie down. Carer's make mistakes - you just need to make sure that it isn't repeated. If the director's attitude to your request is anything other than "sorry, we won't do that again" then you may want to think about placing him elsewhere - but if he is usually OK there then further upheaval at the moment is probably counterproductive.
I agree with Kmn's response. I think this sounds like resonable and rational response. If you don't like the outcome following your requests, consider finding another day care. Unfortuneately you are back to square one when it come to weening off the dummy.