It was a statement,

 

no answer is needed. 

Even if it were a question, it does not have to be answered in the same manner as it was asked.  Teach your child this general rule.  What's the intent of the question?  What's the premise the question was based on?

In this particular situation, one can retort: "So, you are telling me that you are better than me.  Why do you need to do that?"

 

After observing your child's reaction to the taunting and you went home, instead of asking him how he would have come up with an answer, ask him what he felt at that moment, sort out the feelings by naming them: anger, humiliation, or jealousy, etc.. Write each one down and help him analyse the reason for each...  Depending on his age, encouragement should be given to think rationally and not get carried away by feelings.  Thoughts solve problems, feelings don't.