If you cannot defend your side by going over specific facts, talk in generality.
If you cannot defend your side by talking in generality, vouch for your friend.
If you cannot defend your side by vouching for your friend, question critics' motive.
If you cannot defend your side by questioning critics' motive, highlight their ethnic background.
If you still cannot defend your side by highlighting critics' ethnic background, tell everybody you're a PROFESSOR and from........... PRINCETON!