"You look tired."

Someone I work with said this to me the other day. Now is there a worse comment you can make to someone? Isn't this basically the equivalent of telling someone they look awful. This probably wouldn't have bothered me if I actually had been tired, but I didn't feel tired at all that day. And it wasn't even the morning either so it's not like I was still walking around through a "morning daze". So I said, "No. I don't feel tired at all." Then I went and got some coffee.