People who can’t be criticized–and who react with great hostility at any hint of criticism–are revealing something important about themselves.
They reveal that they don’t hold their convictions and viewpoints about various matters through carefully reasoned out, fact-based judgments. Instead, they form conclusions based on emotions. Naturally they feel threatened when one of these irrationally based conclusions is questioned by a thinking mind. In a sense, they expect you to respond to their emotions as they already do: By treating them as equivalent to truth.