Can You Help Me?

     I have a question. You're in a group of friends and you are asked a question--asked to respond honestly. You begin, and a member of the group--one who always is the expert, jumps in, interrupts and asks: "How can you say that? I could never..."
     And you can fill in the blanks as to what he/she says. How do you respond?
     I can say honestly, I don't respond well. Unable to finish my sentence, I listed my credentials--credentials my critic didn't have and would never have, forced out my thoughts and shut up.
     What would you do?