knowledge of good and evil

I was playing Bananagrams with Noah, and I saw some tiles flipped upside down.  I asked him about it.  He said the letters were D, A, and N.  I said, "Why are they face down?" and he looked sheepish and said, "Because I made a bad word."  I said, "How did you ever learn that that was a bad word, and how do you know how to spell it?"  He immediately responded, "How do YOU?"