I wouldn't. Being a parent means being on the receiving end of great emotion -- great love and sometimes great dislike when we deny our kids something they want but clearly don't need. Preschoolers feel things very deeply and are not afraid to tell you what they think. So it's your job to help them learn how to deal with these strong feelings. Let your child know you understand how she feels without condoning what she said: "You are so mad at me for not letting you have a cookie." I would pay little attention to her use of the word "hate," or you'll make the word more powerful for her. However, if you want to try to prevent her from using "hate" again, let her know that the word is not okay and offer other words and ways to express her feelings. For example, she might say, "I am so mad at you!" as she stomps her feet. Sometimes parents have to make unpopular choices, but rest assured, your daughter still loves you, even more than cookies.
Originally published in American Baby magazine, October 2006. Updated 2009