Should they have lied about the cupcakes?

“My brother-in-law wants to open a bakery and he gave me a cupcake to taste test. It was one of the worst cupcakes I had ever had! I told him honestly they were plain and dry. My sister took me outside and said that I was rude and disrespectful and she demanded that I apologize. I refuse to, but my wife wanted to ask your opinion.”