Conversation so far:
What is the Principles of justice?
A Theory of Justice is John Rawls's magnum opus
What is the Liberty Principle in John Rawl's Theoty of Justice?
John Rawl's Liberty Principle establishes equal basic liberties for all citizens.
What is another principle in John Rawl's Theory of Justice?
A Theory of Justice also introduced a two-part second principle comprising Fair Equality of Opportunity and the famous difference principle.

Question: Why is the difference principle controversial?
Self-contained rewrite: Why is John Rawl's difference principle controversial?