"I won't insult your intelligence by suggesting that you really believe what you just said"

This quote by William F. Buckley, Jr. is a subtle method of calling out someone for stating something that is certainly incorrect or misleading. It implies that the individual knows what they are saying is not real, but they are still stating it anyhow. Buckley is indicating that the individual is not being truthful or genuine in their declaration, and he is not ready to accept it as reality. He is essentially stating that he won't be tricked by the person's effort to deceive him. By saying this, Buckley is revealing that he has a high level of intelligence and is not going to be made the most of. He is also showing that he respects the intelligence of the individual he is speaking to, and he will not insult them by assuming they really believe what they just stated.