If that had happened in my daycare they wouldn't have daycare today. I would have terminated them on the spot with no refund of any fees paid.
You need to NOT allow parents to treat you this way. If you worked outside the home would you allow a customer to treat you this way or would you call security or management to have them escorted out? I think you know the answer to that.
YOU set the rules in your daycare. YOU set the tone of respect.
Personally, if it were me, I would be typing up a termination letter today and handing it to them along with all their child's belongings and never allowing them back in my door.